Shock Absorber with Gas Permeable Internal Floating Piston

ABSTRACT

Disclosed herein is a single shock body equipped with the gas permeable internal floating piston. The gas permeable internal floating piston was specifically designed for installation in the multiple stage air shock, the gas permeable internal floating piston being disclosed in the parent application. The gas permeable internal floating piston automatically separates the oil from the gas within the shock body thereby significantly reducing the complexity and cost of manufacturing a shock absorber with the gas permeable internal floating piston. Also, separation is maintained during the operation of the shock throughout the shock&#39;s lifetime. The gas permeable internal floating piston can operate with oils derived from either petroleum or synthetic base stocks, additives, and various gases including dry air, nitrogen, oxygen, carbon monoxide, carbon dioxide, helium, neon, and argon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of, and claims the benefit ofpriority to U.S. patent application Ser. No. 14/940,124, entitled “GasPermeable Internal Floating Piston” filed on Nov. 12, 2015.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTINGCOMPACT DISC APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

The Internal floating piston (IFP) is commonly used to maintainseparation of the oil from the gas during the operation of the shockabsorber. The separation prevents the oil from mixing with the gasthereby significantly improving the dampening characteristics of theshock. Accordingly, the internal floating piston is a highly desirablecomponent in a shock. In order for the internal floating piston to beeffective, the internal floating piston must act as a permanent barrierand the oil and gas must be located on opposite sides of the Internalfloating piston. This requires physically locating the oil and gas onopposite sides of the internal floating piston while charging the shockwith oil and gas. The charging process can be realized either during orafter the construction of the shock. Charging of the shock duringconstruction complicates the construction and increases themanufacturing costs. Charging of the shock after constructionnecessitates two valves (e.g., two Schrader valves); one for oil andanother for gas. This also complicates the construction and increasesthe manufacturing costs and requires an additional step to charge theshock with oil and gas.

In the case of air shocks, the increased work and costs prohibitinternal floating pistons from being used. To date, all commerciallyavailable air shocks operate with emulsion based dampeningcharacteristics because no shock absorber manufacturer installs internalfloating pistons in air shocks (see Fred Williams, Air ShockTechnical-Air Shocks 4 Rocks, non-patent references).

Since the gas permeable internal floating piston is able to separate theoil from the gas and maintain that separation during the operation ofthe shock, then utilization of the gas permeable internal floatingpiston in place of an ordinary internal floating piston promises simplerconstruction, reduced manufacturing costs, and easier set-up methods forthe shock. These benefits and other related benefits are disclosedherein.

Disclosed in patent application Ser. No. 13/854,055 is the multiplestage air shock; and, disclosed in patent application Ser. No.14/935,423 is a process for constructing the multiple stage air shockwhereby the process introduces several features including thedetermination of various lengths and spring rates that are absent in theart. The multiple stage air shock possesses both dampening andsuspension spring capabilities whereby the dampening capability is basedon an emulsion comprised of a mixture of oil and gas.

The emulsion is well known in the art and is considered to provideunpredictable dampening properties in a shock absorber, which in turn,lead to unpredictable handling characteristics for the vehicle. Thedeficiency of the emulsion lies in the mixing of the oil with the gas.The mixing permits the gas to alter the movement of the oil through theworking piston whereby the movement of the oil through the workingpiston defines the dampening properties. One of the techniques used toimprove the dampening properties of an emulsion based shock absorber isto prevent the oil from mixing with the gas, in effect eliminate theemulsion, which is achieved by simply separating the oil from the gas.

A common method of separating the oil from the gas is by installing aninternal floating piston into the working tube of the shock absorber.The oil and gas are placed on opposing sides of the internal floatingpiston thereby effectively separating the oil from the gas. Such amethod represents the basis for a shock absorber known as the monotubeshock absorber whereby the monotube shock absorber is revered for itsdampening properties. In a monotube shock absorber, the oil can beseparated from the gas by attaching check valves to each end of theworking tube whereby the check valve serves to add the oil and gas tothe working tube. Then the oil is added via one check valve while thegas is added via the other check valve. This addition process serves toplace the oil and gas on opposing sides of the internal floating piston.

Such an addition process is not realistic for the multiple stage airshock. The multiple stage air shock involves interconnecting componentsthat serve in a manner like a working tube. However, one of the ends ofone interconnecting component travels into another interconnectingcomponent during the operation of the air shock, and therefore, is notavailable for receiving a check valve. A more realistic method wouldinvolve the addition of the oil and gas into the interconnectingcomponent via a single check valve and then separating the oil from thegas in an autonomous fashion. In this case, the autonomous fashionrefers to the selection of materials used in the construction of theinternal floating piston. In principle, an internal floating piston thatallows the gas but not the oil to pass through its structure wouldrepresent a viable means to separate the oil from the gas. This meansserves as the basis for the present invention.

BRIEF SUMMARY OF THE INVENTION

The present invention extends the gas permeable internal floating pistonto the single shock body, or shock absorber. The gas permeable internalfloating piston defines an effective means of achieving and maintainingseparation of the oil from the gas without the additional manufacturingcosts for a shock absorber of comparable performance.

The present invention offers a novel internal floating piston intendedfor use with the multiple stage air shock. The dampening properties ofthe multiple stage air shock are based on an emulsion comprised of amixture of an oil and gas. The internal floating piston is uniquelycapable of separating the oil from the gas, and in turn, changing thedampening properties of the multiple stage air shock.

The present invention also offers an internal floating piston that:

improves the dampening characteristics of the shock by maintaining theseparation of the oil and gas over the life of the shock;

can operate with various oils. The oils are derived from eitherpetroleum or synthetic base stocks and can include additives thatprovide the oil with specific properties;

can operate with various gases, including nitrogen, oxygen, carbonmonoxide, carbon dioxide, helium, neon, and argon;

is constructed with a gas permeable membrane whereby the membranepermits the gas but not the oil to pass through the structure of theinternal floating piston. This passage serves to separate the oil fromthe gas;

operates autonomously with the use of a spring, the spring serves tocreate a pressure differential across the structure of the internalfloating piston whereby the pressure differential serves to inducepassage of the gas through the structure thereby separating the oil fromthe gas;

moves in conjunction with the shaft during both compression andextension of the shaft the movement, particularly during extension, is aconsequence of restricting permeation of the gas throughout theoperation of the shaft, the restriction achieved by utilizing a membranewith a slow rate of permeation;

improves the dampening properties of each stage in the air shock bymaintaining the separation of the oil and gas throughout the operationof each stage in the air shock;

serves to shorten the extended length, but has no effect on the springrate, of the air shock.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING Brief Descriptionof the Drawings

For purposes of discussion, the internal floating piston is abbreviatedas IFP. It is appreciated that these drawings depict only illustratedembodiments of the invention and are therefore not limited to theprecise arrangements and instrumentalities shown:

FIG. 1 is a side perspective view of the solid wall in the IFP;

FIG. 2 is a side perspective view of the porous bottom in the IFP;

FIG. 3 is a side perspective view of the gas permeable membrane;

FIG. 4 is a side perspective view of inside of the porous cup in theIFP;

FIG. 5 is a side perspective view of outside of the porous cup in theIFP;

FIG. 6 is a side perspective view of the gas permeable IFP;

FIG. 7 is a side plan view of the shock;

FIG. 8 is a side perspective view of the shock;

FIG. 9 is a side plan view of the shock being compressed;

FIG. 10 is a side plan view of the shock being extended;

FIG. 11 is a side plan view of the shock is a fully compressedcondition;

FIG. 12 is a side plan view of the shock is a fully extended condition;

FIG. 13 is a side perspective view of FIG. 5;

FIG. 14 is a side perspective view of FIG. 6;

FIG. 15 is a side plan view of the shock in a right-side up orientation;

FIG. 16 is a side plan view of the shock in an up-side down orientation;

FIG. 17 is a side plan view of the up side down oriented fullycompressed shock;

FIG. 18 is a side plan view of the up side down oriented fully extendedshock, and emphasizes purging the shock with gas;

FIG. 19 is a side plan view of the up side down oriented fully extendedshock, and emphasizes the oil charge in the one cell with purge gas inthe other cell;

FIG. 20 is a side plan view of the up side down oriented fully extendedshock that is charged with oil, and emphasizes the net flow of gasthrough the internal floating piston from the other cell to the one celldue to the shock being charged with gas;

FIG. 21 is a side plan view of the up side down oriented fully extendedshock that is charged with oil and the gas;

FIG. 22 is a side plan view of the right side up oriented fully extendedshock that is charged with oil and the gas, and emphasizes the force ofthe spring pushing the internal floating piston downward;

FIG. 23 is a side plan view of the right side up oriented fully extendedshock that is charged with oil and the gas, and emphasizes the net flowof gas through the internal floating piston from the one cell to theother cell due to the downward motion of the IFP;

FIG. 24 is a side plan view of the right side up oriented fully extendedshock that is charged with oil and the gas, and emphasizes the locationof the oil in the one cell and the gas in the other cell;

FIG. 25 is a side plan view of the right side up oriented partiallyextended shock that is charged with oil and the gas, and emphasizes theforce of the spring constantly pushing the internal floating pistondownward;

FIG. 26 is a side plan view of the IFP, and emphasizes the shape of thecup;

FIG. 27 is a plan view of the outer side of the IFP and emphasizes themembrane;

FIG. 28 is a side perspective view of the IFP;

FIG. 29 is a side plan view of the IFP and emphasizes the properties ofthe IFP;

FIG. 30 is a side plan view of the installation of the IFP in a stage,the one component of the stage is a dual function shaft;

FIG. 31 is a side plan view of the installation of the IFP in a stage,the one component of the stage is a single function shaft;

FIG. 32 is a side perspective view of FIG. 5;

FIG. 33 is a side perspective view of FIG. 6;

FIG. 34 is a side plan view of the IFP equipped stage undergoingcompression;

FIG. 35 is a side plan view of the IFP equipped stage undergoingextension;

FIG. 36 is a side plan view of the IFP equipped stage at fullcompression, and emphasizes the dimensions of the parts of the stage;

FIG. 37 is a side plan view of the IFP equipped stage at full extension,and emphasizes the dimensions of the parts of the stage;

FIG. 38 is a side perspective view of the IFP equipped stage at fullcompression;

FIG. 39 is a side perspective view of the IFP equipped stage at fullextension;

FIG. 40 is a close-up partial plan view of the working piston in thestage and emphasizes the mechanism of dampening during compression;

FIG. 41 is a close-up partial plan view of the working piston in thestage and emphasizes the mechanism of dampening during extension;

FIG. 42 is a side plan view of a monotube shock at full extension, andemphasizes the placement of check valves on each end of the workingtube;

FIG. 43 is a side plan view of a four stage air shock at fullcompression, and emphasizes the placement of a single check valve oneach end cap;

FIG. 44 is a close-up partial plan view of the space in the IFP equippeddual function shaft and emphasizes the machining of channels in the walland end cap of the shaft;

FIG. 45 is a side plan view of the fully extended springless IFPequipped stage, and emphasizes the right side up orientation of thestage;

FIG. 46 is a side plan view of the fully extended springless IFPequipped stage, and emphasizes the up side down orientation of thestage;

FIG. 47 is a side plan view of the up side down oriented fullycompressed springless IFP equipped stage, and emphasizes the oil chargein the one cell;

FIG. 48 is a side plan view of the up side down oriented fully extendedspringless IFP equipped stage, and emphasizes the oil and gas charges inthe one cell;

FIG. 49 is a side plan view of the right side up oriented fully extendedspringless IFP equipped stage that is charged with oil and gas, andemphasizes the force of gravity pulling the IFP downward;

FIG. 50 is a side plan view of the right side up oriented partiallyextended springless IFP equipped stage that is charged with oil and gas,and emphasizes the force of magnetism pulling the IFP downward;

FIG. 51 is a side plan view of the up side down oriented fullycompressed IFP equipped stage;

FIG. 52 is a side plan view of the up side down oriented fully extendedIFP equipped stage, and emphasizes purging the stage with gas;

FIG. 53 is a side plan view of the up side down oriented fully extendedIFP equipped stage, and emphasizes the oil charge in the one cell withgas in the other cell;

FIG. 54 is a side plan view of the up side down oriented fully extendedIFP equipped stage that is charged with oil, and emphasizes the net flowof gas through the IFP from the other cell to the one cell due to thestage being charged with gas;

FIG. 55 is a side plan view of the up side down oriented fully extendedIFP equipped stage that is charged with oil and gas;

FIG. 56 is a side plan view of the right side up oriented fully extendedIFP equipped stage that is charged with oil and the gas, and emphasizesthe force of the spring pushing the IFP downward;

FIG. 57 is a side plan view of the right side up oriented fully extendedspringless IFP equipped stage that is charged with oil and gas, andemphasizes the net flow of gas through the IFP from the one cell to theother cell due to the downward motion of the IFP;

FIG. 58 is a side plan view of the right side up oriented fully extendedIFP equipped stage that is charged with oil and the gas, and emphasizesthe net flow of gas through the IFP from the one cell to the other celldue to the downward motion of the IFP;

FIG. 59 is a side plan view of the right side up oriented fully extendedspringless IFP equipped stage that is charged with oil and gas, andemphasizes the forces of gravity and magnetism constantly pulling theIFP downward;

FIG. 60 is a side plan view of the right side up oriented fully extendedIFP equipped stage that is charged with oil and the gas, and emphasizesthe location of the IFP due to the fully extended spring;

FIG. 61 is a side plan view of the right side up oriented partiallyextended IFP equipped stage that is charged with oil and the gas, andemphasizes the force of the spring constantly pushing the IFP downward;

FIG. 62 is a side plan view of the fully extended IFP equipped stagethat is charged with oil and gas, and emphasizes the origin of the IFPand working piston prior to displacement;

FIG. 63 is a side plan view of the slightly compressed IFP equippedstage that is charged with oil and gas, and emphasizes the displacementof the IFP and working piston;

FIG. 64 is a side plan view of the mostly compressed IFP equipped stagethat is charged with oil and gas, and emphasizes the displacement of theIFP and working piston;

FIG. 65 is a side plan view of the fully compressed IFP equipped stagethat is charged with oil and gas, and emphasizes the displacement of theIFP and working piston along with other dimensions of the stage;

FIG. 66 is an equation that computes the areas of the component andshaft;

FIG. 67 is an equation that computes the change in volume of the othercell and shaft in terms of the displacements of the IFP and workingpiston, respectively;

FIG. 68 is an equation that shows the relationship among the change involume of the other cell, change in volume of the gas, and change involume of the shaft;

FIG. 69 is an equation that shows the relationship between thedisplacement of the working piston and change in shaft stroke;

FIG. 70 is an algorithm that shows the relationship between thedisplacements of the IFP and working piston, the displacements being dueto the compression of the shaft;

FIG. 71 is a side plan view of the fully extended four stage air shockthat is equipped with the IFP in each stage;

FIG. 72 is a side plan view of the fully compressed four stage air shockthat is equipped with the IFP in each stage;

FIG. 73 is a side perspective view of the fully extended four stage airshock that is equipped with the IFP in each stage;

FIG. 74 is a side perspective view of the fully compressed four stageair shock that is equipped with the IFP in each stage;

FIG. 75 is a side plan view of the four stage air shock that is equippedwith the IFP in each stage whereby the stages are in various states ofcompression/extension;

FIG. 76 is a side perspective view of the four stage air shock that isequipped with the IFP in each stage whereby the stages are in variousstates of compression/extension;

FIG. 77 is a side plan view of the fully extended IFP equipped fourstage air shock, and emphasizes the right side up orientation of theshock;

FIG. 78 is a side plan view of the fully extended IFP equipped fourstage air shock, and emphasizes the up side down orientation of theshock;

FIG. 79 is a side plan view of the up side down oriented fullycompressed IFP equipped four stage air shock;

FIG. 80 is a side plan view of the up side down oriented fully extendedIFP equipped four stage air shock, and emphasizes purging each stagewith gas;

FIG. 81 is a side plan view of the up side down oriented fully extendedIFP equipped four stage air shock, and emphasizes the oil charge in eachstage;

FIG. 82 is a side plan view of the up side down oriented fully extendedIFP equipped four stage air shock that is charged with oil, andemphasizes the net flow of gas through the IFP from the other cell tothe one cell due to each stage being charged with gas;

FIG. 83 is a side plan view of the up side down oriented fully extendedIFP equipped four stage air shock that is charged with oil and gas;

FIG. 84 is a side plan view of the right side up oriented fully extendedIFP equipped four stage air shock that is charged with oil and the gas,and emphasizes the force of the spring pushing the IFP downward;

FIG. 85 is a side plan view of the right side up oriented fully extendedIFP equipped four stage air shock that is charged with oil and the gas,and emphasizes the net flow of gas through the IFP from the one cell tothe other cell due to the downward motion of the IFP;

FIG. 86 is a side plan view of the right side up oriented fully extendedIFP equipped four stage air shock that is charged with oil and the gas,and emphasizes the location of the IFP due to the fully extended spring;

FIG. 87 is a side plan view of the fully extended IFP equipped fourstage air shock in which each stage is charged with oil and gas and theoil and gas occupy one and the other cells;

FIG. 88 is a side plan view of the fully compressed IFP equipped fourstage air shock in which each stage is charged with oil and gas and theoil and gas occupy one and the other cells;

FIG. 89 is a side plan view of the IFP equipped four stage air shock inwhich each stage is charged with oil and gas and the oil and gas occupyone and the other cells whereby the stages are in various states ofcompression/extension;

FIG. 90 is a side plan view of the fully extended IFP equipped fourstage air shock, and emphasizes the dimensions of the shock and partsfor each stage;

FIG. 91 is a side plan view of the fully compressed IFP equipped fourstage air shock, and defines the compressed length of the shock;

FIG. 92 is an equation that computes the length of the working tubeL_(X) for the multiple stage air shock comprising X stages wherebyX=2-7;

FIG. 93 is an equation that computes the lengths of the nth dual roleshafts L_(Wn) for the multiple stage air shock comprising X stages wheren=1, 2, . . . , X−1 and X=2-8;

FIG. 94 is an equation used to compute the shaft stroke for the firststage L_(S1) for the multiple stage air shock comprising X stages whereX=1-8;

FIG. 95 is an equation that computes the shaft stroke for the nth stageL_(S2-8) for the multiple stage air shock comprising X stages where n=2,3, . . . , X and X=2-8;

FIG. 96 is an equation that computes the compressed length CL_(X) forthe multiple stage air shock comprising X stages where X=1-8;

FIG. 97 is an equation that computes the extended length EL_(X) for themultiple stage air shock comprising X stages where X=1-8;

FIG. 98 shows the selected value for the mounting eyelet me;

FIG. 99 is an equation that relates the value for the thickness of thenth IFP to that for the nth working piston where n=1-8;

FIGS. 100-107 are tables of the selected values for wp_(n), ss_(n), andec_(n) for the nth stage for the multiple stage air shock comprising Xstages where n=1, 2, . . . , X and X=1-8;

FIG. 108 is a table of the computed values for L_(X), L_(W1-7),L_(S1-8), CL_(X), EL_(X), and EL_(X)/CL_(X) for the multiple stage airshock comprising X stages where X=1-8 and L₁ is a selected value;

FIG. 109 is a plan view of the fully compressed IFP equipped stage thatcomprises a component and shaft;

FIG. 110 is a plan view of the fully compressed IFP equipped stage thatcomprises a component and shaft and emphasizes the volumes of the oiland gas;

FIG. 111 is an equation that computes the area of the first, second,third, or fourth stage, A_(n);

FIG. 112 is an equation that computes the volume of the shaft stroke forthe first, second, third, or fourth stage, V_(n);

FIG. 113 is an equation that computes the volume of the gas charge forthe first, second, third, or fourth stage, V_(Gt);

FIG. 114 is an equation that computes the constant in Boyle's Law forthe first, second, third, or fourth stage, c_(t);

FIG. 115 is an equation that computes the shaft stroke at ride heightfor the first, second, third, or fourth stage, L_(t);

FIG. 116 is an equation that computes the volume of the shaft stroke atride height for the first, second, third, or fourth stage, V_(t);

FIG. 117 is an equation that computes the gas charge at ride height forthe first, second, third, or fourth stage, P_(Gt);

FIG. 118 is an equation that computes the volume of the stage at theselected incremental shaft stroke for the first, second, third, orfourth stage, V_(Z);

FIG. 119 is an equation that computes the gas pressure at the selectedincremental shaft stroke for the first, second, third, or fourth stage,P_(Z);

FIG. 120 is an equation that computes the suspension force at theselected incremental shaft stroke for the first, second, third, orfourth stage, F_(Z);

FIG. 121 is an equation that computes the spring rate at the selectedincremental shaft stroke for the first, second, third, or fourth stage,SR_(Z);

FIG. 122 is an equation that computes the percent change in incrementalshaft stroke at the selected incremental shaft stroke for the first,second, third, or fourth stage, % ΔL_(Z);

FIG. 123 is a table of the selected values for the diameter, D_(n),shaft stroke, L_(n) suspension force at ride height, F_(t), and percentchange in shaft stroke at ride height, % L_(t), where n refers to thefirst, second, or third dual function shaft or single function shaft andt refers to the first, second, third, or fourth stage, respectively;

FIGS. 124-127 are tables of the computed values for % ΔL_(Z), F_(Z),ΔL_(Z), SR_(Z) and selected value for L_(Z) where ΔL_(Z), refers to thechange in incremental shaft stroke at a selected incremental shaftstroke, and L_(Z) refers to the selected incremental shaft stroke andwhere Z=1e, 2f, 3g, or 4h for the first, second, third, or fourth stage,respectively;

FIG. 128 is a graph of the curved lines of suspension force F₁₋₄ vschange in incremental shaft stroke ΔL₁₋₄ for the first, second, third,and fourth stages;

FIG. 129 is a graph of the curved lines of suspension force F₁₋₄ vschange in incremental shaft stroke ΔL₁₋₄ for the first, second, third,and fourth stages in which a dotted line is traced over a part of eachcurved line.

DETAILED DESCRIPTION OF THE INVENTION

Detailed herein is the installation of the gas permeable internalfloating piston in a single shock body, otherwise called a shockabsorber or simply a shock. Emphasis is placed on the novel advantagesof the gas permeable internal floating piston over an ordinary internalfloating piston. Hereafter, the gas permeable internal floating pistoncan be called our gas permeable internal floating piston.

Our gas permeable internal floating piston comprises two components, agas permeable membrane and an internal floating piston. Conversely, anordinary internal floating piston comprises only one component, aninternal floating piston. The ordinary internal floating piston lacks agas permeable membrane or any other type of membrane. Therefore, the gaspermeable membrane enables our gas permeable internal floating piston toseparate the oil from the gas within the shock body while the ordinaryinternal floating piston cannot separate the oil from the gas at anylocation or time.

Our internal floating piston is made out of the same type of material asis an ordinary internal floating piston including plastic, plasticcomposite, aluminum, metal alloy, or carbon fiber. However, theconstruction process for our internal floating piston is different fromthat for an ordinary internal floating piston.

The structure of the ordinary internal floating piston is constructed asan impenetrable solid disc such that a substance cannot pass through theordinary internal floating piston's structure. Lack of passage definesthe ordinary internal floating piston as a solid barrier thatpermanently separates the substance (e.g., oil) located on one side ofthe internal floating piston from the substance (e.g., gas) located onthe other side of the internal floating piston.

Referring to FIGS. 1-6, the structure of our internal floating piston isbuilt like a porous cup 11. The porous cup 11 is constructed from twocomponents: a cylinder-like solid wall 11 c and a porous bottom 11 d.The solid wall has the one and second ends, the one and second endsrefer to the inner and outer sides 11 a and 11 b of the internalfloating piston, respectively. The porous bottom 11 d has the shape andhard, rigid structure of a fritted disc. The porous bottom 11 d isattached to the second end of the solid wall 11 c, i.e., attached to theouter side 11 b of the internal floating piston. The attachment of theporous bottom 11 d to the solid wall 11 c gives the internal floatingpiston the shape of a cup. The structural strength and integrity of theporous cup 11 is far superior to that of the solid wall 11 c or porousbottom 11 d alone thereby enhancing the structural integrity anddurability of the internal floating piston. The gas permeable membrane12 is attached to one side of the porous bottom 11 d, the one sidereferring to the outer side 11 b of the internal floating piston. Thehard, rigid structure of the porous bottom 11 d supports the gaspermeable membrane 12 thereby enhancing the structural integrity anddurability of the gas permeable membrane 12. The combinations of the gaspermeable membrane 12 being attached to the porous bottom 11 d and ofthe porous bottom 11 d being attached to the solid wall 11 c define ourgas permeable internal floating piston 10.

The cylinder-like solid wall is specifically designed for two purposes:one purpose is the same as that of an ordinary internal floating pistonwhile the second purpose is novel to our internal floating piston. Theone purpose is to act as a seal against the inside of the shock body inorder to maintain separation of the oil from the gas. The novel secondpurpose is to enable our internal floating piston to slide into and outof the shock body in conjunction with the sliding motion of the shaft.Conversely, an ordinary internal floating piston is shaped more like adisc than a cylinder and is designed to shift back and forth within theshock body but not to slide into and out of the shock body. The shiftingaccounts for the slight change in volume within the shock body due tothe movement of the shaft. The diameter of the shaft in an ordinaryshock is small such that the sliding of the shaft into and out of theshock body causes only a slight change in volume that must be accountedfor by the gas. The diameter of the shaft in an air shock is large suchthat the sliding of the shaft into and out of the shock body causes alarge change in volume that must be accounted for by the gas. Since ourgas permeable internal floating piston was specifically designed tooperate in an air shock, our internal floating piston is able to slideinto and out of the shock body in conjunction with the sliding motion ofthe shaft. Recall that no shock absorber manufacturer currently installsinternal floating pistons in air shocks.

The porosity of the bottom is a function of the construction process notthe type of material the bottom is made of, the material being metallic,plastic (see Discs, Porous Metal Discs; and, Filtration Catalogue,Porvair Plastic Battery Vents; both citations located in non-patentreferences), or other material like that used in constructing the solidwall. The porosity defines the “fritting” in a fritted disc whereby thefritting is the sintering together of particles into a solid but porousobject such that there are pore spaces located throughout the objectlike a sponge. Substances are able to pass through the object by passingthrough the pore spaces. Sintering is the process of compacting andforming a solid mass of material by heat or pressure without melting itto the point of liquefaction. The porous bottom serves the same purposeas does the fritted disc used by Qin in U.S. Pat. No. 8,419,961; namely,a support for the gas permeable membrane that is porous to gases suchthat gases can pass through the pore spaces.

The gas permeable membrane is able to be attached to the porous bottomwith an adhesive, the adhesive is an amorphous polymer selected from thegroup consisting of an organic solution of TFE/PFD copolymer, an aqueoussolution of PTFE or PFEP particulate dispersion, and an organic solutionof PTFE or PFEP particulate dispersion with 0.05-5 .mu.m in particlesize (see Qin in U.S. Pat. No. 8,419,961). The adhesive forms acoalesced porous network whereby the gas permeable membrane and adhesivecooperate with the porous bottom such that a gas can pass through theporous bottom. The membrane is permeable to gases but impermeable toliquids. The permeability of the membrane and porosities of the adhesiveand bottom cooperate such that gases are able to pass from one side ofthe gas permeable internal floating piston to the other side whileliquids are prevented from passing through the gas permeable internalfloating piston. The gas permeable internal floating piston is animpenetrable barrier against liquids.

Our gas permeable membrane is a type of semi-permeable membrane.Semi-permeable membranes define the state of the art in separating onesubstance from another, and are widely used in a diverse array ofindustries including the medical, petrochemical, water treatment,textile, transportation, agriculture, forestry, defense, andenvironmental sciences (see Koltuniewicz, The History And State Of ArtIn Membrane Technologies, non-patent references). In the petrochemicalindustry, gas-permeable membranes are used to separate dissolved gasesfrom the bulk petroleum crude oil during the refining process. Suchmembrane separation has proven to be technically and economicallysuperior to other technologies (see Abedini, Application Of Membrane InGas Separation Processes: Its Suitability And Mechanisms, non-patentreferences). In the transportation industry, semi-permeable membranesare used in the remediation of waste water during the cleaning processand in the recovery of the pigment-coating during the electrophoreticpainting process (see Koltuniewicz, The History And State Of Art InMembrane Technologies, non-patent references). Gas permeable membraneshave been utilized in more specialized applications. For example: inU.S. Pat. No. 5,749,942, Mattis discloses a method of making a compositemembrane in which a very thin layer of an amorphousperfluoro-2,2-dimethyl-1,3-dioxole polymer is sandwiched between aperforated metal plate or a wire screen or mesh. The method is used toseparate fault gases from the oil in electrical transformers; in U.S.Pat. No. 8,419,961, Qin discloses a method in which a gas permeablemembrane that is attached to a fritted disc is used to perform the samefunction as does Mattis' method. Qin's method improves upon Mattis'method by enabling, among other features, the gas to be detected andmonitored under harsher temperature and pressure conditions; and, inU.S. Pat. No. 8,197,578, Hruby discloses that a gas permeable membraneis used to separate gases from the liquid propellant in rocket motors.The separation removes gas bubbles that may form in the propellant; and,the gas bubbles can interrupt the flow of fuel, resulting in a stall orloss of control of the motor.

Beyond the uses of semi-permeable membranes in the transportationindustry as noted above, there is no known application of asemi-permeable membrane in the automobile industry. Specifically, ourapplication of a gas permeable membrane in a shock absorber isunprecedented. A gas permeable membrane or our gas permeable internalfloating piston defines a solid structure with “no moving parts, makingthem mechanically robust and increasing their suitability for use inremote locations where reliability is critical” (see Freeman, GasSeparation Using Polymers, non-patent references). Our gas permeablemembrane and internal floating piston are constructed from materialsthat can withstand the operating conditions inside the body of a shockabsorber, including high temperatures and pressures. Our gas permeablemembrane is similar to that used by Qin (see U.S. Pat. No. 8,419,961).Qin discloses that his gas permeable membrane is made from a bulkpolymer material that can withstand harsh temperature and pressureconditions. Silicon based gas permeable membranes are known to survivepressures as high as 1300 psi and temperature ranges from −95 to 400degrees Fahrenheit (see SSP-M823, Polydimethyl Silicone Membrane,non-patent references). During operation of the shock, if temperaturesrise noticeably above that suitable for the bulk polymer material, thenour gas permeable membrane can be constructed from other materials,e.g., ceramic membranes. Materials that are thermally stable attemperatures above 400° C. (752 degrees Fahrenheit) include ceramicmembranes that are used to separate hydrogen from gasified coal (seeAbedini, Application Of Membrane In Gas Separation Processes: ItsSuitability And Mechanisms, non-patent references). Our internalfloating piston is made of the same materials as an ordinary internalfloating piston; therefore it can clearly withstand the operatingconditions inside the body of a shock absorber.

Gas permeable membranes are very thin; e.g., in U.S. Pat. No. 8,419,961,Qin uses a bulk polymer material with a thickness ranging from 0.01-0.5mm, which is 0.0004-0.020 inches. The durability of a gas permeablemembrane is related to the cross-sectional thickness of the membrane. Asthickness increases, the membrane's durability increases andpermeability decreases (see Freeman, Gas Separation Using Polymers;Montoya, Membrane Gas Exchange; and, Abedini, Application Of Membrane InGas Separation Processes: Its Suitability And Mechanisms; all citationslocated in non-patent references). The capability to maintain separationof the gas and oil during the operation of the shock absorber increasesas the rate of gas permeation of the membrane decreases. Therefore, arelatively thick membrane improves both the performance and durabilityof a gas permeable membrane in a shock absorber, and thereby defines akey design feature of our gas permeable membrane. The durability of agas permeable membrane in a shock absorber is more a function oftemperature than pressure. Pressure becomes an issue only when thepressure on one side of the membrane is different than that on the otherside of the membrane, i.e., the creation of a pressure differentialacross the structure of the membrane. Too great of a pressuredifferential can rupture the membrane, thereby causing the membrane tofail.

In response to road obstructions, the rapid movement of the shaft cancreate rapid changes in pressure in the shock body. The pressure changeis not significant in an ordinary shock due to the relatively smalldiameter of the shaft. An insignificant pressure change indicates aninsignificant pressure differential across the structure of themembrane, and therefore has no practical impact on the gas permeablemembrane. Instead, the pressure change is significant only in an airshock due to the relatively large diameter of the shaft. However, thecompliant movement of our internal floating piston in reaction to themovement of the shaft ensures that the change in pressure on one side ofthe membrane is essentially the same as that on the other side of themembrane. Therefore when equipped with our gas permeable internalfloating piston, the operation of the air shock creates insignificantpressure differential across the structure of the membrane, therebyindicating that pressure has no practical impact on the gas permeablemembrane. Instead, a spring can be used to create sufficient pressuredifferential across the structure of our gas permeable internal floatingpiston in order to invoke separation of the gas from the oil in anyshock, be it an ordinary or air shock.

Our gas permeable membrane is a synthetic bulk polymer made of materialincluding poly(tetrafluoroethylene),poly(tetrafluoroethylene-co-hexafluoropropylene), poly(vinylidenefluoride), poly(tetrafluoroethylene-co-perfluoro alkoxy vinyl ether),polydimethylsiloxane derivatives, poly (1-trimethylsilyl-1-propyne)derivatives, polyethylenes, polypropylenes, polysulfones, polyimides,polymethacrylates, or silicic-acid heteropolycondensates (see Qin, U.S.Pat. No. 8,419,961. See also Freeman, Gas Separation Using Polymers;Kossov, Novel fluorine-functionalized 1,2-disubstitutedpolyacetylene—Poly(1-(3,3,3-trifluoropropyldimethylsilyl)-1-propyne).Synthesis, microstructure and gas transport properties; and, Abedini,Application Of Membrane In Gas Separation Processes: Its Suitability AndMechanisms; all citations located in non-patent references).

The gas permeability of the membrane is a molecular process in whichindividual gas particles travel through the membrane, a particle beingan atom or a molecule comprised of two of more covalently bonded atoms.Permeation can occur at any point on the cross-sectional area of themembrane; meaning that an enormous number (at least trillions) of gasparticles can pass through the membrane at any given moment. The processincludes at least three distinct steps: adsorption of the gas particlesto the outer surface of one side of the membrane, diffusion of the gasparticles through the membrane, and desorption of the gas particles fromthe outer surface of the other side of the membrane. (see Qin, U.S. Pat.No. 8,419,961. See also Freeman, Gas Separation Using Polymers; and,Abedini, Application Of Membrane In Gas Separation Processes: ItsSuitability And Mechanisms; both citations located in non-patentreferences). The permeability to gases and impermeability to liquidsdefines permeability on the basis of the phase of the substance: the gaspermeable membrane is permeable to substances in the gas phase andimpermeable to substances in the liquid phase. This means that anysubstance that is in the gas phase can permeate through the membranewhile any substance that is in the liquid phase cannot permeate throughthe membrane.

-   -   Specifically, our gas permeable membrane is permeable to gases        and impermeable to liquids at any temperature and pressure that        does not compromise the integrity of the material that the        membrane is made from, as discussed above. The thermal expansion        or contraction of the liquid due to a significant increase or        decrease in temperature has no effect on the liquid        impermeability of our gas permeable membrane, respectively.

The mechanism of permeation is derived from either a solution/diffusionpathway or size exclusion pathway. If the membrane is made from a densebulk polymer, then the membrane lacks pores and permeation occurs viathe solution/diffusion pathway. The gas dissolves into the membrane,diffuses through the membrane, and then evaporates out of the membrane;adsorption defines dissolution while desorption defines evaporation. Ifthe membrane is made from a porous bulk polymer, then the membrane haspores and permeation occurs via the size exclusion pathway. The gasparticles are much smaller than the liquid particles such that the gasparticles can pass between the pore spaces in the membrane via theadsorption, diffusion, desorption process.

A shock equipped with the gas permeable internal floating piston canoperate with oils derived from petroleum base stocks, synthetic basestocks, or a blend of both stocks (see Hydraulic Fluids, Chemical andPhysical Information; Article Archives, Conventional vs Synthetic Oi;Safety Data Sheet, Shock Therapy Suspension Fluid-Amsoil; and SafetyData Sheet, Synthetic Suspension Fluids-Redline Synthetic Oil, allcitations located in non-patent references). If the oil is derived frompetroleum base stocks, then the oil is a paraffin-based hydrocarbonconsisting of at least 20-34 carbon atoms and 40-68 hydrogen atoms; thehydrocarbon includes long-chain alkanes, cycloalkanes, or theirunsaturated analogs. If the oil is derived from synthetic base stocks,then the oil can be made from a number of chemical bases and classes ofcompounds consisting of at least 15-50 carbon atoms and includesalkylated aromatics, olefin polymers, dibasic acid esters, neopentylpolyesters, poly glycols, phosphate esters, silicones, silicate esters,fluoro carbons, and/or poly phenyl ethers.

Substrates are commonly added to the petroleum and synthetic base stocksin order to furnish the oil with specific properties, including: organicsulfur-, phosphorus-, and chlorine-containing compounds, which helpprevent surface damage under severe loading; fatty acids andderivatives, and organophosphate esters, which prevent wearing underlight loads; fatty acids, sulfonates, and salts of fatty acids, whichprevent corrosion by oxygen and water; phenols, amines, and sulfides,which inhibit oxidation of the oil; silicone oils, which prevent foamformation; polyalphaolefins, polymethacrylates, and polyalkylstyrenes,which reduce the dependence of viscosity on temperature;polymethacrylates and condensation products, which lower the pour pointtemperature; ionogenic and nonionogenic polar compounds, which allowseparation of oil and water; and sulfonates and amides, which preventunwanted deposits (see Hydraulic Fluids, Chemical and PhysicalInformation, non-patent references).

A shock equipped with the gas permeable internal floating piston canoperate with gases derived from dry air; second row elements such asnitrogen, oxygen, carbon monoxide, and carbon dioxide; and noble gasessuch as helium, neon, and argon (see Montoya, Membrane Gas Exchange; andFreeman, Gas Separation Using Polymers; both citations are located innon-patent references). In general, nitrogen is by far the most commongas used in shocks. Specialized gases such as nitric oxide, nitrousoxide, nitrogen dioxide, carbon disulfide, and sulfur dioxide can beused but are toxic or corrosive and not recommended. Other gases such ashydrogen and volatile hydrocarbons (e.g., methane, ethylene, ethane,propane, butane, and pentane) can be used but are flammable and notrecommended.

Construction of the shock with an ordinary internal floating piston iscomplex and includes charging the shock with oil and gas. Charging canbe effected either during or after the shock is constructed: (1) duringconstruction, the machine that charges the shock with gas must be housedin an enclosure that is isolated from the atmosphere. To preventmoisture from contaminating the gas, the enclosure must be purged of allgases/atmosphere. Then the machine must charge the working tube with thegas in such a manner that the gas is confined to the working tube underhigh pressure. Separate and additional steps must be included to insertthe internal floating piston into the working tube, followed by chargingthe working tube with oil. The simplest construction process wouldinvolve a multiple step approach in which the internal floating pistonis inserted partway into the working tube such that two separatechambers are formed in the working tube. Then one of the chambers mustbe purged of moisture followed by charging the chamber with the gas athigh pressure. Another step would involve charging the other chamberwith oil; and (2) after construction, the internal floating piston mustbe positioned within the working tube such that the working tubecomprises two separate chambers, the chambers being on opposite sides ofthe internal floating piston. The shock must be constructed with twovalves such that one of the valves connects to one chamber while thesecond valve connects to the second chamber. The chamber specified forthe gas must first be purged of moisture and then the shock can becharged with the gas via the one valve. Afterwards, the shock can becharged with the oil via the second valve. The charging steps must beperformed in a manner such that the gas is able to be added under highpressure.

The process of constructing the shock with two valves and a properlypositioned internal floating piston such that the working tube comprisestwo separate chambers prior to the charging steps significantlyincreases the complexity and cost of manufacturing a shock with anordinary internal floating piston.

Far and away, the predominant benefit of a shock equipped with the gaspermeable internal floating piston is the simplified manufacturingprocesses and reduced costs of the shock. The manufacturing processesand steps required to construct the shock with the gas permeableinternal floating piston are no different than that for a shock withoutan internal floating piston other than the additional step of insertingthe gas permeable internal floating piston into the working tube priorto the shaft. Following construction, the shock is charged with oil andgas, and then, after giving the membrane a bit of time to separate theoil from the gas, is ready to be installed on the vehicle.

Clearly, an important benefit of equipping the shock with the gaspermeable internal floating piston is that it promises dampeningcharacteristics equal to a shock with an ordinary internal floatingpiston. Since the oil and gas are permanently separated in a shock withthe gas permeable internal floating piston, the shock with the gaspermeable internal floating piston delivers state-of-the-art dampeningperformance just like the shock with an ordinary internal floatingpiston. And the shock with the gas permeable internal floating pistondelivers this performance at a cost that is marginally greater than thatfor a shock without an internal floating piston, and significantly lessthan that for a shock with an ordinary internal floating piston. Inprinciple, the cost can be as little as the sum of the construction costof the shock plus the material cost for the gas permeable internalfloating piston. Since the gas permeable membrane enables automaticseparation of the oil from the gas, there are no additional costsassociated with the specialized construction and charging of a shockthat is equipped with an ordinary internal floating piston.

Just as important is that the shock with the gas permeable internalfloating piston is able to retain this state-of-the-art level ofperformance throughout the lifetime of the shock. As a shock ages, thegas may be able to leak out of its chamber and into the oil chamberthereby diminishing an ordinary internal floating piston's ability tomaintain separation of the oil and gas. The leakage acts to contaminatethe oil and converts the oil into an oil/gas emulsion. The emulsionerodes the dampening characteristics of the shock thereby eliminatingthe purpose of the ordinary internal floating piston—in effect,converting a shock with an ordinary internal floating piston into ashock without an internal floating piston. Since the gas permeableinternal floating piston possesses the unique capability of separatingthe oil from the gas, the problem of leakage becomes a non-problem. Anyleaked gas permeates through the gas permeable internal floating pistonout of the oil chamber and back into the gas chamber. Quite simply,permeation serves to maintain internal floating piston dampeningcharacteristics throughout the lifetime of the shock.

Referring to FIGS. 7-14, there are shown the shock with the gaspermeable internal floating piston. The shock comprises a working tube15, shaft 17, gas permeable internal floating piston 10, working piston18, end cap 19, valve 20, and two mounting eyelets 14. The working tube15 has a closed end 23 and an open end, a mounting eyelet 14 is attachedto the closed end 23 while the end cap 19 is attached to the open end.The shaft 17 has two closed ends, a mounting eyelet 14 is attached toone end while the working piston 18 is attached to the other end. Thegas permeable internal floating piston 10 is inserted into the workingtube 15 followed by the working piston 18. The working tube 15 has twospaces 21 and 22, space 21 is between the end cap 19 and gas permeableinternal floating piston 10 while space 22 is between the gas permeableinternal floating piston 10 and closed end 23. A spring 13 is able to beattached to the gas permeable internal floating piston 10.

Referring to FIGS. 15-25, there is shown the process of separating theoil from the gas. FIGS. 15 and 16 show the shock when the shock isoriented right-side up and up-side down, respectively. FIG. 17 shows theshock when its oriented up-side down and fully compressed. FIG. 18 showsthe shock filled with gas to purge moisture from working tube 15, thegas being at atmospheric pressure. FIG. 19 shows the shock charged withoil. FIG. 20 shows the shock being charged with gas whereby the highpressure of the gas charge forces the gas permeable internal floatingpiston 10 to move downward thereby compressing the spring 13 andinducing the atmospheric gas to pass through the gas permeable internalfloating piston 10, bubble up through the oil, and collect with the gascharge. FIG. 21 shows the shock charged with gas whereby both the oiland gas occupy cell 21 with the gas being located above the oil. FIG. 22shows the shock oriented right-side up such that the spring 13 begins toextend thereby forcing the gas permeable internal floating piston 10 tomove downward. FIG. 23 shows the shock whereby the downward motion ofthe gas permeable internal floating piston 10 induces the gas to passthrough the gas permeable internal floating piston 10 from cell 21 intocell 22. FIG. 24 shows the shock in a fully extended condition wherebythe spring 13 is fully extended with all the gas having passed throughthe gas permeable internal floating piston 10 such that the oil occupiescell 21 while the gas occupies cell 22. FIG. 25 shows the shock slightlycompressed such that it's not in the fully extended condition wherebythe spring 13 exerts a constant downward force on the gas permeableinternal floating piston 10; the constant downward force induces any gasthat leaks from cell 22 into cell 21 to pass through the gas permeableinternal floating piston 10 such that the leaked gas returns back intocell 22.

Described below is a gas permeable internal floating piston specificallydesigned for installation in the multiple stage air shock. The multiplestage air shock is disclosed in patent application Ser. No. 13/854,055whereby a process for constructing the multiple stage air shock isdisclosed in patent application Ser. No. 14/935,423. The internalfloating piston features a gas permeable membrane that has a slow rateof permeation; the permeability serves to separate the oil from the gaswhile the slow rate of permeation permits the internal floating pistonto move in conjunction with the shaft during the operation of the airshock. To facilitate understanding of the present invention, themultiple stage air shock is described; and then exemplified with thefour stage air shock.

Referring to FIGS. 26-29, the internal floating piston 10 is illustratedin detail. The internal floating piston 10 has a composite constructionthat includes a cup 11 and gas permeable membrane 12. The cup 11 is madefrom metal alloy or plastic with a solid wall, porous bottom with innerand outer sides 11 a and 11 b, and is able to be associated with aspring 13. The wall represents a cylindrical surface that facilitatesthe sliding motion of the internal floating piston 10 within the spaceof the working tube or dual function shaft in the same manner as doesthe working piston. The cylindrical surface and porous bottom give theinternal floating piston 10 the structure of a porous cup whereby thestructure gives the internal floating piston 10 a thickness ip. Theinner bottom of the cup 11 refers to the inner side 11 a of the internalfloating piston 10 while the outer bottom of the cup 11 refers to theouter side 11 b of the internal floating piston 10. The membrane 12 isattached to the outer side 11 b of the internal floating piston 10 andis permeable to gases but not liquids. The porous bottom of the cup 11cooperates with the permeable membrane 12 such that the internalfloating piston 10 is permeable to the gas but not the oil whereby theinternal floating piston 10 being permeable to the gas indicates thatthe gas is able to pass through the structure of the internal floatingpiston 10. The permeation mechanism is: adsorption of the gas into themembrane 12, diffusion of the gas across the membrane 12, and desorptionof the gas from the membrane 12. The permeation of the gas across themembrane 12 defines the permeation of the gas through the structure ofthe internal floating piston 10 and is governed by the presence of apressure differential across the inner and outer sides 11 a and 11 b ofthe internal floating piston 10. The spring 13 is constructed from steelwire and has short and long ends whereby the short end is attached tothe inner side 11 a of the internal floating piston 10 while the longend is able to be butted up against the closed end of the working tubeor dual function shaft.

Referring to FIGS. 30-39, there is shown the installation of theinternal floating piston 10 in a stage. The stage refers to thefundamental shock unit in the multiple stage air shock. The multiplestage air shock includes a working tube and two or more shafts, workingpistons, and end caps. The stage consists of the one and secondinterconnected components whereby the one component is the dual orsingle function shaft 16 or 17 while the second component is the workingtube 15 or dual function shaft 16.

The working tube 15 has the one and second ends whereby the one end isclosed and the second end is open such that the closed end is attachedto a mounting eyelet while the open end is attached to the end cap 19.The end cap 19 serves as a seal in a manner like a torus gasket.

The one or second component is able to define a shaft and has the oneand second ends whereby the type of the shaft is defined by the type ofthe ends the shaft has: the one end is closed and the second end iseither closed or open. The one end is attached to the working piston 18.When the second end is closed, the second end is attached to themounting eyelet and the one component is a single function shaft 17;whereas when the second end is open, the second end is attached to theend cap 19 and the one or second component is a dual function shaft 16.

The working piston 18 has a disk and shims whereby the disk contains alarge hole in the center and smaller surrounding holes. The center holepermits the working piston 18 to be attached to the one component. Theshims have varying holes, diameters, and thicknesses whereby the shimsare arranged sequentially on each side of the disk.

The interconnection between the one and second components refers to theone closed end of the one component being slidably inserted into theopen end of the second component whereby the one component sliding intoor out of the second component refers to the one component beingcompressed or extended, and thereby refers to the stage being compressedor extended, respectively. The compression or extension of the stagerefers to the operation of the stage and is caused by suspension forcesacting on the stage. The insertion defines a space within the secondcomponent whereby the space is between the closed end and end cap 19,has a volume, and refers to a volume of the stage. The end cap 19 isequipped with a check valve 20 whereby the check valve 20 permits oiland gas to be added to or removed from the stage. The addition of agiven amount of oil or gas refers to the oil or gas charge,respectively. The oil and gas occupy the space such that the sealingaction of the end cap 19 confines the oil and gas to the space wherebythe confinement allows the oil to have a volume and gas to have both avolume and pressure. The gas pressure is related to the gas charge anddefines a force whereby the force is able to be a suspension springforce. The suspension spring force provides the stage with a suspensionspring capability thereby enabling the stage both to support part of theweight of the vehicle and to react to suspension movements.

Assembling the stage involves: first, the internal floating piston 10 isslidably inserted into the open end of the second component thereby theinternal floating piston 10 is enabled to slide within the secondcomponent under guidance by the solid wall of the internal floatingpiston 10 whereby the long end of the spring 13 is butted up against theclosed end of the second component; and second, the one component isslidably inserted into the open end of the second component whereby theone and second components are able to belong to one and another stages,respectively. The internal floating piston 10 divides the space withinthe second component into the one and second cells 21 and 22,respectively, such that the one cell 21 is between the outer side 11 bof the internal floating piston 10 and end cap 19 while the second cell22 is between the inner side 11 a of the internal floating piston 10 andclosed end 23 of the second component whereby the spring 13 is locatedin the second cell 22. The space has a volume such that the volumedefines the volumes of the one and second cells 21 and 22, the volumesof the one and second cells 21 and 22 refers to the volume of the stage.

Referring to FIGS. 34 and 35, during the operation of the stage both theinternal floating piston 10 and one component move in the same directionsuch that during compression, the internal floating piston 10 slidestowards the closed end of the second component while the one componentslides into the second component; whereas during extension the internalfloating piston 10 slides away from the closed end of the secondcomponent while the one component slides out of the second component.Referring to FIGS. 36 and 37, the dimensions of the stage are shownincluding: diameter and length of the second component D_(W) and L_(W),diameter and length of the one component D_(S) and L_(WS), shaft strokeL_(S), and thicknesses of the internal floating piston ip, workingpiston wp, shaft shoulder ss, end cap ec, and mounting eyelet me,respectively.

Referring to FIGS. 40 and 41, there is shown the mechanism of dampeningby the working piston 18, in this case emphasizing the process ofcharging a stage with oil and gas. For purposes of discussion: (1) thestage comprises the shaft S and component C whereby the shaft S refersto the dual or single function shaft 16 or 17 while the component Crefers to the working tube 15 or dual function shaft 16; and (2) theworking piston 18 has a disk 24 and shims 25 and 26, and is locatedbetween the fastener 27 and shaft shoulder 28 whereby the fastener 27attaches the working piston 18 to the shaft S. The shims 25 and 26 arearranged sequentially on each side of the disk 24 such that the shims 25are located next to the fastener 27 while the shims 26 are located nextto the shaft shoulder 28.

Since the working piston 18 is attached to the shaft S, the workingpiston 18 moves in concert with the shaft S as the shaft S slides intoor out of the component C: referring to FIG. 40, the dashed arrows showthat the working piston 18 is sliding into the component C therebyindicating that the stage is undergoing compression; while referring toFIG. 41, the dashed arrows show that the working piston 18 is slidingout of the component C thereby indicating that the stage is undergoingextension. The motion of the working piston 18 causes the oil to flowthrough the holes in the disk 24 and shims 25 and 26: referring to FIGS.40 and 41, the shaded dotted line boxes define the holes in the disk 24and shims 25 and 26. The solid arrows show that: during compression, theoil flows into the holes in the shims 25, through the holes in the disk24, and out of the holes in the shims 26, and then into the passageway29 between the shaft S and cylinder wall of the component C; whileduring extension, the oil flows out of the passageway 29 between theshaft S and cylinder wall of the component C and into the holes in theshims 26, through the holes in the disk 24, and out of the holes in theshims 25.

The flow of the oil through the holes causes the working piston 18 toresist the sliding of the shaft S whereby the resistance acts to dampenthe suspension spring motion of the stage. The suspension spring motionof the stage refers to the suspension spring capability of the stagewhereby the suspension spring capability of the stage is provided by thegas pressure. The emulsion that results from the mixing of the oil andgas is known to cause the dampening ability of the working piston tovary unpredictably whereby the unpredictable dampening results inunpredictable handling for the vehicle. The installation of the internalfloating piston 10 into the component C offers the ability to separatethe oil from the gas in the component C whereby this separation preventsthe mixing of the oil and gas and leads to predictable dampening.Predictable dampening leads to predictable reactions by the shock tosuspension forces which in turn results in predictable handling for thevehicle.

Referring to FIG. 42, there is shown a representation of a commonmonotube shock that is comprised of one working tube 15, single functionshaft 17, and internal floating piston 10. The oil can be easilyseparated from the gas by utilizing one and a second check valves 20 aand 20 b—the one check valve 20 a is mounted to the closed end 23 of theworking tube 15 while the second check valve 20 b is mounted to end cap19. The one check valve 20 a is used only for adding the oil while thesecond check valve 20 b is used only for adding the gas. Since theinternal floating piston 10 is located within the space between theclosed end 23 of the working tube 15 and end cap 19, this method ofaddition naturally leads to the oil occupying the one cell 21 betweenthe end cap 19 and internal floating piston 10 while the gas occupiesthe second cell 22 between the closed end of the working tube 15 andinternal floating piston 10.

Referring to FIG. 43, there is shown a four stage air shock in whicheach stage is fully compressed; each stage is equipped with the internalfloating piston 10. The closed end 23 of each dual function shaft 16 isinserted into the interconnecting component and therefore is notavailable for receiving a check valve 20. Since each end cap 19 remainsoutside the interconnecting component at all times during the operationof each stage, then only the end cap 19 is able to receive a check valve20. Both the oil and gas must be added to each stage via the check valve20 that is mounted to each end cap 19. A logical alternative wouldrequire some type of channel to be machined within the cylinder wall ofeach dual function shaft 16 from each end cap 19 to the closed end 23 ofeach dual function shaft 16. The interconnecting component refers to theworking tube 15 or dual function shaft 16.

Referring to FIG. 44, there is shown a close-up view of a stage thatcomprises a dual function shaft 16 and shaft S, in this case emphasizingboth a shaded channel 30 that is machined into the cylinder wall of thedual function shaft 16 and a shaded channel 31 that is machined into theend cap 19. One and a second check valves 20 a and 20 b are mounted tothe end cap 19. The channel 30 connects a hole in the closed end 23 ofthe dual function shaft 16 to the one check value 20 a while the channel31 connects a hole in the end cap 19 to the second check value 20 b. Theone check valve 20 a vents to the second cell 22 because the one checkvalve 20 a is connected to the second cell 22 via the channel 30 that ismachined into the cylinder wall of the dual function shaft 16; while thesecond check valve 20 b vents to the one cell 21 because the secondcheck valve 20 b is connected to the one cell 21 via the channel 31 thatis machined into the end cap 19.

Cooperation between the channel 31 and second check valve 20 brepresents the normal means by which oil and gas are added to or removedfrom the space within a stage in the multiple stage air shock. The oilwould be added via the second check valve 20 b in the normal manner intothe one cell 21 thereby locating the oil between the end cap 19 andinternal floating piston 10. Meanwhile the gas could be added via theone check valve 20 a and channel 30 into the second cell 22 therebylocating the gas between the closed end 23 of the dual function shaft 16and internal floating piston 10. The additions serve to locate the oiland gas on opposite side of the internal floating piston 10 and therebyseparate the oil from the gas. However, the process of machining achannel 30 within the wall of a thin-walled cylinder is not realistic.As a practical matter, both the oil and gas must be added via the secondcheck valve 20 b. Following the addition of the oil and gas, the oilmust be separated from the gas autonomously within the space of thestage. The present invention suggests three different methods ofeffecting this autonomous separation whereby this autonomous separationrefers to the operation of the internal floating piston 10.

Note: referring to FIG. 43, in the four stage air shock the working tube15 could be equipped with another check valve at the closed end 23 inaddition to the check valve 20 that is attached to the end cap 19; andtherefore, oil and gas can be separated as discussed for the commonmonotube shock. For purposes of discussion, the working tube 15 istreated in the same manner as each dual function shaft 16.

Referring to FIGS. 45-61, there is shown the stage that is equipped withthe internal floating piston 10, in this case emphasizing the process ofthe internal floating piston 10 separating the oil and gas into the oneand second cells, respectively. For purposes of discussion: (1) the dualfunction shaft 16 and single function shaft 17 and are referred to asthe component 16 and shaft 17, respectively, whereby the component 16refers to the working tube 15 or dual function shaft 16 while the shaft17 refers to the dual function shaft 16 or single function shaft 17, (2)referring to FIG. 45, the stage is oriented right side up whereby thestage is in a vertical position such that the closed end 23 of thecomponent 16 is at the top of the space while the end cap 19 of thecomponent 16 is at the bottom of the space whereby the one cell 21 isbelow the internal floating piston 10 while the second cell 22 is abovethe internal floating piston 10; and, referring to FIG. 46, the stage isoriented upside down whereby upside down is the opposite of right sideup, and (3) the internal floating piston 10 is not attached to thespring 13 except as noted in method 3 below. The space within thecomponent 16 contains the internal floating piston 10 whereby theinternal floating piston 10 divides the space into the one and secondcells 21 and 22. The oil and gas are able to occupy opposite sides ofthe internal floating piston 10 such that the oil occupies the one cell21 while the gas occupies the second cell 22. The process of separatingthe oil and gas into the one and second cells 21 and 22 involves twosteps: in step one, the stage is charged with oil and gas such that boththe oil and gas occupy the one cell 21; and in step two, the gaspermeable membrane 12 is utilized in conjunction with a pressuredifferential. The membrane 12 allows the gas but not oil to pass throughthe structure of the internal floating piston 10 while the creation of apressure differential across the sides of the internal floating piston10 serves as the force that induces a net flow of gas through thestructure of the internal floating piston 10 from the one cell 21 intothe second cell 22.

The pressure differential can be created with at least three methods:the process of charging the stage with oil and gas in methods 1 and 2 isdifferent than that for method 3, therefore step one for methods 1 and 2is discussed separately from that for method 3.

Step One for methods 1 and 2: Referring to FIG. 47, the stage isoriented upside down such that the end cap 19 of the component 16 is atthe top of the space while the closed end 23 of the component 16 is atthe bottom of the space. The shaft 17 is fully compressed such that theworking piston 18 pushes the internal floating piston 10 against theclosed end 23 whereby the space within the component 16 consists of theone cell 21 only. The stage is charged with oil and gas through thecheck valve 20 that is located on the end cap 19: first the oil chargeis added thereby filling up the one cell 21 whereby a small amount ofair occupies the cup 11 in the structure of the internal floating piston10 and is ignored; second referring to FIG. 48, the gas charge is addedwhereby the shaft 17 fully extends to accommodate the gas, and the spacewithin the component 16 consists of the one cell 21 only whereby the onecell 21 is positioned above the internal floating piston 10 while theinternal floating piston 10 is still bottomed out against the closed end23 of the component 16. Since the oil and gas are immiscible, the oildoes not mix with the gas and since the oil and gas occupy the one cell21, the oil locates next to the gas such that the surface of the oilcontacts that of the gas whereby the contacting surfaces are defined asthe interface. The locations of the oil and gas at the interface aredefined by density such that the more dense oil will locate below theinterface next to the internal floating piston 10 while the less densegas will locate above the interface next to the end cap 19. Afteraddition of the gas charge, the stage is rotated 180 degrees to theright side up orientation such that the closed end 23 of the component16 is at the top of the space while the end cap 19 of the component 16is at the bottom of the space; the one cell 21 is below the internalfloating piston 10 such that the oil will locate below the interfacenext to the end cap 19 while the gas will locate above the interfacenext to the internal floating piston 10. For method 1; referring to FIG.49, the internal floating piston 10 is heavy enough that it slidesdownward in the space within the component 16, the force of gravityF_(V) acting to pull the internal floating piston 10 downward againstthe gas. For method 2; referring to FIG. 50, the working piston 18 andinternal floating piston 10 are constructed in a manner such that theypossess strong permanent magnetic properties. Upon insertion into thespace within the component 16, the internal floating piston 10 ispositioned such that it is magnetically attracted to the working piston18. Slow compression of the shaft 17 either by mechanical means or byinstalling the shock on a vehicle and cycling the suspension through itsrange of travel will act locate the working piston 18 close to theinternal floating piston 10, the close proximity between the workingpiston 18 and internal floating piston 10 serves to create a strongattractive magnetic interaction between the working piston 18 andinternal floating piston 10, the interaction between the working piston18 and internal floating piston 10 causes a magnetic force F_(M) thatacts to pull the internal floating piston 10 downward against the gas.

Step One for method 3: the short end of the spring 13 is attached to theinner side 11 a of the internal floating piston 10 and then the internalfloating piston 10 is inserted into the component 16 such that the longend of the spring 13 is butted against the closed end 23 of thecomponent 16. Referring to FIG. 51, the stage is oriented upside downsuch that the end cap 19 of the component 16 is at the top of the spacewhile the closed end 23 of the component 16 is at the bottom of thespace, and the shaft 17 is fully compressed such that the internalfloating piston 10 bottoms out against the closed end 23 of thecomponent 16, the location of the internal floating piston 10 serves tofully compress the spring 13. Referring to FIG. 52, gas is added suchthat the shaft 17 fully extends whereby fully compressing the stage andthen adding gas serves to purge the space within the component 16 of themoisture that is in the air; the small amount of air occupying the cup11 of the internal floating piston 10 is not purged and is ignored. Theprocess of fully extending the shaft 17 allows the spring 13 that isattached to the internal floating piston 10 to also fully extend wherebythe gas, at atmospheric pressure, occupies both the one and second cells21 and 22, respectively. Referring to FIG. 53, the component 16 ischarged with oil whereby the fully extended spring 13 positions theinternal floating piston 10 in a manner such that the addition of theoil charge acts to fill up the one cell 21 whereby the gas in the secondcell 22 is at atmospheric pressure.

Referring to FIGS. 54 and 55, the component 16 is charged with gaswhereby the more dense oil will locate below the interface next to theinternal floating piston 10 while the less dense gas charge will locateabove the interface next to the end cap 19, the one cell 21 now containsboth the oil and gas charges. The pressure of the gas charge exerts aforce on the oil whereby the oil is non-compressible while the internalfloating piston 10 is impermeable to the oil thereby enabling the oil totransfer the force against the internal floating piston 10. The pressureof the gas charge is greater than atmospheric pressure while the forceof the gas pressure is greater than that of the spring thereby enablingthe force of the gas pressure to cause the internal floating piston 10to slide downward, the downward motion of the internal floating piston10 compresses the spring 13, decreases the volume of the second cell 22,and increases the pressure of the gas in the second cell 22; thedownward motion continues until the pressure of the gas in the secondcell 22 is the same as that of the gas charge. Since the density of thegas is less than that of the oil, the gas in the second cell 22 willexert a force F_(UP) that acts upward against the internal floatingpiston 10. Since the internal floating piston 10 is permeable to thegas, the upward force F_(UP) defines an increase in pressure next to theinner side 11 a of the internal floating piston 10 while there is nochange in pressure next to the outer side 11 b of the internal floatingpiston 10. The pressure imbalance defines a pressure differential acrossthe structure of the internal floating piston 10 whereby the pressuredifferential induces a net flow of gas G_(F) through the structure ofthe internal floating piston 10 from the second cell 22 and into the onecell 21. As soon as the gas from the second cell 22 passes through theinternal floating piston 10 into the one cell 21, the gas is able tobubble upward through the oil and accumulate with the gas charge that isnext to the end cap 19 whereby the gas from the second cell 22 and gascharge are hereafter referred to as the gas. The combination of the flowof the gas G_(F) through the structure and the force of the gas pressurebeing greater than that of the spring 13 causes the internal floatingpiston 10 to continue sliding downward until the internal floatingpiston 10 bottoms out against the closed end 23 of the component 16. Theforce of the gas pressure holds the internal floating piston 10 againstthe closed end 23 of the component 16 whereby the location of theinternal floating piston 10 fully compresses the spring 13. The spacewithin the component 16 consists of the one cell 21 only.

Note: After the oil charge is added but before the gas charge is added,the oil is heavier than the gas that is in the second cell 22 therebyresulting in a difference in density between the oil and gas. Thisdifference in density will allow the gas to exert a force that actsupward against the internal floating piston 10. Since the internalfloating piston 10 is permeable to the gas, the upward force will serveto create a pressure differential across the sides of the internalfloating piston 10 such that the gas is induced to flow through thestructure of the internal floating piston 10 from the second cell 22 andinto the one cell 21. However, this flow of gas is ignored because theforce associated with the difference in density is insufficient tocompress the spring 13. The spring 13 would necessarily have to becompressed in order to account for the increase in volume of the onecell 21 and equivalent decrease in volume of the second cell 22 thatwould result from the flow of gas through the structure of the internalfloating piston 10. In particular, the downward motion of the internalfloating piston 10 only compresses the spring 13 and does not create apressure differential that induces the flow of gas G_(F) through thestructure of the internal floating piston 10 from the second cell 22 andinto the one cell 21. The force of the gas pressure that causes thedownward motion of the internal floating piston 10 is due to the gaspressure next to the outer side 11 b being greater than that next to theinner side 11 a which is opposite the increase in pressure next to theinner side 11 a with no change in pressure next to the outer side 11 b.The increase in pressure next to the inner side 11 a with no change inpressure next to the outer side 11 b defines the pressure differentialthat serves to induce the flow of gas G_(F) through the structure of theinternal floating piston 10 from the second cell 22 and into the onecell 21.

Referring to FIG. 56, the stage is rotated 180 degrees to the right sideup orientation such that the closed end 23 of the component 16 is at thetop of the space while the end cap 19 of the component 16 is at thebottom of the space whereby the more dense oil is below the interfacenext to the end cap 19 while the less dense gas is above the interfacenext to the internal floating piston 10. Since the internal floatingpiston 10 is permeable to the gas, the gas is able to flow through theinternal floating piston 10. The ability to flow indicates that theforce of the gas pressure is able to have no effect on the internalfloating piston 10, and instead acts against the closed end of thecomponent 16. The absence of the effect cancels the force of the gaspressure against the internal floating piston 10; therefore the internalfloating piston 10 is no longer held against the closed end 23 of thecomponent 16. Since the internal floating piston 10 is no longer heldagainst the closed end 23 of the component 16, the spring 13 that isattached to the internal floating piston 10 begins to extend exertingthe force F_(SP) against the internal floating piston 10 such that theinternal floating piston 10 pushes downward against the gas.

Step Two: Referring to FIG. 57 for methods 1 and 2, and FIG. 58 formethod 3, the downward motion M_(D) of the internal floating piston 10creates a greater pressure zone next to the outer side 11 b of theinternal floating piston 10 while an equivalent lower pressure zone iscreated next to the inner side 11 a of the internal floating piston 10.Again the pressure imbalance defines the pressure differential acrossthe structure of the internal floating piston 10, the pressuredifferential induces the net flow of gas G_(F) through the structure ofthe internal floating piston 10 from the one cell 21 and into the secondcell 22 such that the oil occupies the one cell 21 and the gas occupiesthe second cell 22.

Referring to FIGS. 59 and 60, the forces F_(V) and F_(M) created bygravity and magnetism in methods 1 and 2 and the fully extended spring13 in method 3 will serve to constantly hold the internal floatingpiston 10 at the interface; in particular the forces F_(V) and F_(M)created in methods 1 and 2 are constantly exerted on the internalfloating piston 10 and in turn the internal floating piston 10 transfersthe forces F_(V) and F_(M) against the oil, respectively. Referring toFIG. 61, since both the shaft 17 and spring 13 that is attached to theinternal floating piston 10 are fully extended when the one cell 21 isfilled up with oil and since the oil is non-compressible, then any forcethat acts to compress the shaft 17 from full extension will also serveto compress the spring 13; in effect anytime the shaft 17 is not in thefully extended position, the spring 13 will be compressed, andtherefore, will exert a force F_(SP) against the internal floatingpiston 10 and in turn the internal floating piston 10 transfers theforce F_(SP) against the oil. Since the downward forces F_(V), F_(M),and F_(SP) are constantly acting against the oil, then so long as thestage is oriented right side up the more dense oil will remain below theinterface in the one cell 21 and the less dense gas will remain abovethe interface in the second cell 22 while the internal floating piston10 remains at the interface and maintains separation of the oil and gas,regardless of the stroke of the shaft 17 or pressure of the gas.

While the methods 1-3 are each capable of maintaining separation of theoil and gas during the operation of the stage, the present inventionfocuses on the method 3. Henceforth, all subject matter is based on theprinciples discussed in method 3.

Referring to FIGS. 62-70, there are shown the stage that is equippedwith the internal floating piston 10, in this case emphasizing themotion of the internal floating piston 10 during the operation of thestage. For purposes of discussion, (1) the single function shaft 17 iscalled a shaft 17 and refers to the dual or single function shaft whilethe dual function shaft 16 is called a component 16 and refers to theworking tube or dual function shaft, (2) road obstructions definesuspension forces that are exerted on the stage while the gas pressuredefines a force that counteracts the suspension force, and (3) thevolume of the gas G occupying the cup of the internal floating piston 10is ignored:

Referring to FIGS. 62-65, there is shown the stage undergoingcompression. During the operation of the stage, suspension forces areexerted on the stage thereby causing the stage to compress; whereas whenthe suspension forces are reduced, the force of the gas pressurecounteracts the suspension force and causes the stage to extend: (1)during compression, suspension forces are exerted on the stage therebycausing the shaft 17 to slide into the component 16. The suspensionforces that are exerted on the shaft 17 are transferred to the oil.Since the internal floating piston 10 is not permeable to the oil, thenthe suspension forces that are exerted on the oil are transferred to theinternal floating piston 10 thereby causing the internal floating piston10 to slide towards the closed end of the component 16. The motion ofthe internal floating piston 10 decreases the volume of the second cellwhereby the decrease in the volume serves to increase the gas pressure;(2) during extension, the suspension forces exerted on the stage arereduced, in turn, the suspension forces exerted on the shaft 17 arereduced, in turn, the suspension forces that are transferred to the oilare reduced, in turn, the suspension forces that are transferred to theinternal floating piston 10 are reduced. Since the internal floatingpiston 10 is permeable to the gas but not the oil, then in principle thegas is able to flow through the internal floating piston 10. The abilityto flow indicates that the force of the gas pressure is able to have noeffect on the internal floating piston 10. The absence of the effectindicates that the force of the gas pressure does not act on theinternal floating piston 10, and instead the gas pressure exerts a forcedirectly on the oil; this way when the suspension forces that aretransferred to the internal floating piston 10 are reduced, the force ofthe gas pressure that is exerted on the oil is transferred to the shaft17 thereby causing the shaft 17 to slide out of the component 16.

During extension, the shaft 17 slides out of the component 16 and awayfrom the internal floating piston 10. In principle, the motion of theshaft 17 serves to create a low pressure zone next to the outer side 11b of the internal floating piston 10 while the gas pressure serves tocreate a high pressure zone next to the inner side 11 a of the internalfloating piston 10. The resulting pressure differential induces a netflow of gas through the structure of the internal floating piston 10from the second cell and into the one cell. Since the motion of theshaft 17 is able to be very rapid, then the internal floating piston 10must also be able to move very rapidly in conjunction with the shaft 17in order for the internal floating piston 10 to remain at the interfaceand maintain separation of the oil and gas. Such rapid motion by theinternal floating piston 10 can be realized by utilizing a membrane 12that possesses a slow permeation rate. During the rapid extension of theshaft 17, the slow permeation rate indicates that the gas is able toremain in the second cell such that the pressure of that gas is able toexert a force against the internal floating piston 10 thereby causingthe internal floating piston 10 to move while very little, if any, ofthe gas will permeate across the internal floating piston 10. Inreaction to suspension forces, the movement of the shaft 17 can occur onthe order of fractions of a second while the slow permeation rate of thegas occurs on the order of minutes. During the operation of the stage,the shaft 17 can undergo numerous of cycles of compression and extensionwithin a minute. For example, assume one cycle occurs every second whilethe gas permeates across the internal floating piston 10 in 5 minutes,then: (a) in one minute, the shaft 17 will have cycled 60 times whileonly 20% of the gas will be able to permeate across the internalfloating piston 10, (b) in three seconds, the shaft 17 will have cycled3 times while only 1% of the gas will be able to permeate across theinternal floating piston 10, and (c) in one second during any givencycle, at least 99% of the gas will remain in the second cell such thatthe pressure of that gas will exert a force against the internalfloating piston 10 thereby causing the internal floating piston 10 tomove while at most 1% of the gas will be able to permeate across theinternal floating piston 10. Moreover only 50% of those cycles, i.e.,the extension movements, require the slow permeation rate of themembrane 12 to keep the gas in the second cell because the remaining 50%of those cycles, i.e., the compression movements, will serve to push theinternal floating piston 10 against the spring 13, in turn, the spring13 compresses thereby creating the pressure differential that serves toinduce the net flow of gas through the internal floating piston 10 fromthe one cell and into the second cell. In effect, once the internalfloating piston 10 separates the oil and gas such that they occupy theone and second cells, then the oil and gas will remain separated by theinternal floating piston 10 during the operation of the stage.

As a practical matter, during extension the force of the gas pressure isexerted on the internal floating piston 10 rather than directly on theoil. Therefore the force of the gas pressure that is exerted on theinternal floating piston 10 is transferred to the oil, in turn, theforce of the gas pressure that is exerted on the oil is transferred tothe shaft 17 thereby causing the shaft 17 to slide out of the component16. The slow permeation rate of the membrane 12 ensures that the oil andgas remain separated and occupy the one and second cells, respectively,thereby ensuring that the force of the gas pressure is exerted on theinternal floating piston 10 such that the internal floating piston 10rapidly slides away from the closed end of the component 16 and moves inconjunction with the shaft 17.

The motion of the shaft 17 causes a change in the volume of the spacewithin the component 16, the volume of the space define the volumes ofthe one and second cells while the one and second cells define thevolume of the stage. Since the oil occupies the one cell and isnon-compressible, then the volume of the one cell remains constant; and,results in the change in the volume of the space within the component 16referring to the change in the volume of the second cell ΔV_(IFP), i.e.,the change in the volume of the space within the component 16 is thesame as the change in the volume of the second cell ΔV_(IFP). Therefore,the change in the volume of the second cell ΔV_(IFP) defines the changein the volume of the stage. Since the gas occupies the second cell, thenthe change in the volume of the space within the component 16 refers tothe change in the volume of the gas ΔV_(G) whereby the change in thevolume of the gas ΔV_(G) is the same as the change in the volume of thesecond cell ΔV_(IFP). Since the motion of the shaft 17 causes the changein the volume of the space within the component 16, then the change inthe volume of the shaft stroke ΔV_(S) refers to the change in the volumeof the space within the component 16. In summary, the change in thevolume of the shaft stroke ΔV_(S) defines the change in the volume ofthe space within the component 16, the change in the volume within thecomponent 16 refers to the change in the volume of the second cellΔV_(IFP), the change in the volume of the second cell ΔV_(IFP) refers tothe change in the volume of the gas ΔV_(G)—in short, the change in thevolume of the shaft stroke ΔV_(S) defines the change in the volume ofthe gas ΔV_(G). Since the change in the volume of the second cellΔV_(IFP) defines the change in the volume of the stage, then the changein the volume of the gas ΔV_(G) defines the change in the volume of thestage.

During the motion of the shaft 17, the working piston 18 and internalfloating piston 10 are displaced. Referring to FIG. 62; starting withthe stage at full extension, then the origins of the displacements areshown as the right-hand side r_(WP) and d_(IFP) of the working piston 18and internal floating piston 10, respectively. The displacements d_(WP)and d_(IFP) of the working piston 18 and internal floating piston 10 aredifferent, respectively: since the working piston 18 is attached to theshaft 17, then the displacement d_(WP) of the working piston 18 is thesame as the change in the shaft stroke ΔL_(S). In contrast, thedisplacement d_(IFP) of the internal floating piston 10 is less than thedisplacement d_(WP) of the working piston 18; the difference being dueto part of the oil flowing into or out of the passageway 29 between theshaft 17 and cylinder wall of the component 16. Referring to FIGS.62-65, as the stage undergoes compression, part of the oil flows intothe passageway 29 between the shaft 17 and cylinder wall of thecomponent 16 whereby this flow reduces the amount of oil between theworking piston 18 and internal floating piston 10—in effect the workingpiston 18 gets closer to the internal floating piston 10. Since theworking piston 18 gets closer to the internal floating piston 10, thenthe internal floating piston 10 is moving slower than the working piston18 and thereby the displacement d_(IFP) of the internal floating piston10 is less than the displacement d_(WP) of the working piston 18.

Referring to FIGS. 66-70, there is shown a set of equations used to findthe relative displacements d_(WP) and d_(IFP) of the working piston 18and internal floating piston 10, respectively. Since the change in thevolume of the second cell ΔV_(IFP) refers to the change in the volume ofthe shaft stroke ΔV_(S), then the relationship between the change in thevolume of the second cell V_(IFP) and that of the shaft stroke V_(S) canbe used to describe the relationship between the displacement d_(IFP) ofthe internal floating piston 10 and displacement d_(WP) of the workingpiston 18. Referring to FIG. 45, the set of equations is used to derivean algorithm that shows that the displacement d_(IFP) of the internalfloating piston 10 is less than the displacement d_(WP) of the workingpiston 18.

In principle, the volume of the gas V_(G) is the sum of the volume ofthe shaft stroke V_(S) plus the volume of the gas G occupying the cup ofthe internal floating piston 10. For purposes of discussion, the volumeof the gas G occupying the cup is ignored; therefore, the volume of thegas V_(G) is the same as the volume of the shaft stroke V_(S). As apractical matter, the difference between the volume of the shaft strokeV_(S) and that of the gas V_(G) that is caused by the volume of the gasG occupying the cup has negligible effect on computations regarding gaspressure particularly those involving spring rate and therefore thisdifference is ignored.

Referring to FIGS. 71-76, there is shown the four stage air shock invarious states of operation, in this case emphasizing the installationof the internal floating piston into each stage of the four stage airshock:

The first stage includes the working tube 32, first dual function shaft33, and first internal floating piston 45. The working tube 32 has aclosed end and an open end whereby the closed end is affixed to amounting eyelet while the open end is attached to a first end cap 41.The first dual function shaft 33 has a closed end and an open endwhereby the closed end is attached to a first working piston 37 whilethe open end is attached to a second end cap 42. The first internalfloating piston 45 has the structure of a porous cup whereby thestructure comprises a solid wall, inner and outer sides, and a firstspring 49; and, the first spring 49 has a short and long ends wherebythe short end is attached to the inner side. The first internal floatingpiston 45 is slidably inserted into the open end of the working tube 32thereby the first internal floating piston 45 is enabled to slide withinthe working tube 32 under guidance by the solid wall whereby the longend of the first spring 49 is butted up against the closed end of theworking tube 32; then, the first dual function shaft 33 is slidablyinserted into the open end of the working tube 32. The process of thefirst dual function shaft 33 being inserted into the working tube 32defines a space within the working tube 32 between the closed end of theworking tube 32 and first end cap 41; whereas, the first internalfloating piston 45 divides the space into the one and second cellswhereby the one cell is between the outer side of the first internalfloating piston 45 and first end cap 41 while the second cell is betweenthe inner side of the first internal floating piston 45 and closed endof the working tube 32. The space has a volume V_(W) which defines thevolumes of the one and second cells whereby the volumes of the one andsecond cells define the volume V_(W) of the first stage. The first endcap 41 is equipped with a check valve 20, the check valve 20 serves as ameans to add oil and gas to or remove oil and gas from the first stage.The first internal floating piston 45 has a gas permeable membranewhereby the membrane is attached to the outer side of the first internalfloating piston 45 and is permeable to gases but not liquids. Thepermeability allows the gas but not the oil to pass through thestructure thereby the first internal floating piston 45 is able toseparate the oil and gas such that the oil is able to occupy the onecell while the gas is able to occupy the second cell. The first end cap41 acts as a seal such that the oil and gas are confined to the one andsecond cells; and the confinement allows the oil to have a volume andgas to have both a volume and pressure whereby the gas pressure definesa force.

The second stage includes the first dual function shaft 33, second dualfunction shaft 34, and second internal floating piston 46. The seconddual function shaft 34 has a closed end and an open end whereby theclosed end is attached to a second working piston 38 while the open endis attached to a third end cap 43. The second internal floating piston46 has the structure of a porous cup whereby the structure comprises asolid wall, inner and outer sides, and a second spring 50; and, thesecond spring 50 has a short and long ends whereby the short end isattached to the inner side. The second internal floating piston 46 isslidably inserted into the first dual function shaft 33 thereby thesecond internal floating piston 46 is enabled to slide within the firstdual function shaft 33 under guidance by the solid wall whereby the longend of the second spring 50 is butted up against the closed end of thefirst dual function shaft 33; then the second dual function shaft 34 isslidably inserted into the first dual function shaft 33. The process ofthe second dual function shaft 34 being inserted into the first dualfunction shaft 33 defines a space within the first dual function shaft33 between the closed end of the first dual function shaft 33 and secondend cap 42; whereas, the second internal floating piston 46 divides thespace into the one and second cells whereby the one cell is between theouter side of the second internal floating piston 46 and second end cap42 while the second cell is between the inner side of the secondinternal floating piston 46 and closed end of the first dual functionshaft 33. The space has a volume V_(W1) which defines the volumes of theone and second cells whereby the volumes of the one and second cellsdefine the volume V_(W1) of the second stage. The second end cap 42 isequipped with a check valve 20, the check valve 20 serves as a means toadd oil and gas to or remove oil and gas from the second stage.

The second internal floating piston 46 has a gas permeable membranewhereby the membrane is attached to the outer side of the secondinternal floating piston 46 and is permeable to gases but not liquids.The permeability allows the gas but not the oil to pass through thestructure thereby the second internal floating piston 46 is able toseparate the oil and gas such that the oil is able to occupy the onecell while the gas is able to occupy the second cell. The second end cap42 acts as a seal such that the oil and gas are confined to the one andsecond cells; and the confinement allows the oil to have a volume andgas to have both a volume and pressure whereby the gas pressure definesa force.

The third stage includes the second dual function shaft 34, third dualfunction shaft 35, and third internal floating piston 47. The third dualfunction shaft 35 has a closed end and an open end whereby the closedend is attached to a third working piston 39 while the open end isattached to a fourth end cap 44. The third internal floating piston 47has the structure of a porous cup whereby the structure comprises asolid wall, inner and outer sides, and a third spring 51; and, the thirdspring 51 has a short and long ends whereby the short end is attached tothe inner side. The third internal floating piston 47 is slidablyinserted into the second dual function shaft 34 thereby the thirdinternal floating piston 47 is enabled to slide within the second dualfunction shaft 34 under guidance by the solid wall whereby the long endof the third spring 51 is butted up against the closed end of the seconddual function shaft 34; then the closed end of the third dual functionshaft 35 is slidably inserted into the second dual function shaft 34.The process of the third dual function shaft 35 being inserted into thesecond dual function shaft 34 defines a space within the second dualfunction shaft 34 between the closed end of the second dual functionshaft 34 and third end cap 43; whereas, the third internal floatingpiston 47 divides the space into the one and second cells whereby theone cell is between the outer side of the third internal floating piston47 and third end cap 43 while the second cell is between the inner sideof the third internal floating piston 47 and closed end of the seconddual function shaft 34. The space has a volume V_(W2) which defines thevolumes of the one and second cells whereby the volumes of the one andsecond cells define the volume V_(W2) of the third stage. The third endcap 43 is equipped with a check valve 20, the check valve 20 serves as ameans to add oil and gas to or remove oil and gas from the third stage.The third internal floating piston 47 has a gas permeable membranewhereby the membrane is attached to the outer side of the third internalfloating piston 47 and is permeable to gases but not liquids. Thepermeability allows the gas but not the oil to pass through thestructure thereby the third internal floating piston 47 is able toseparate the oil and gas such that the oil is able to occupy the onecell while the gas is able to occupy the second cell. The third end cap43 acts as a seal such that the oil and gas are confined to the one andsecond cells; and the confinement allows the oil to have a volume andgas to have both a volume and pressure whereby the gas pressure definesa force.

The fourth stage includes the third dual function shaft 35, singlefunction shaft 36, and fourth internal floating piston 48. The singlefunction shaft 36 has the one and second closed ends whereby the oneclosed end is attached to a fourth working piston 40 while the secondclosed end is affixed to a mounting eyelet. The fourth internal floatingpiston 48 has the structure of a porous cup whereby the structurecomprises a solid wall, inner and outer sides, and a fourth spring 52;and, the fourth spring 52 has a short and long ends whereby the shortend is attached to the inner side. The fourth internal floating piston48 is slidably inserted into the third dual function shaft 35 therebythe fourth internal floating piston 48 is enabled to slide within thethird dual function shaft 35 under guidance by the solid wall wherebythe long end of the fourth spring 52 is butted up against the closed endof the third dual function shaft 35; then the single function shaft 36is slidably inserted into the third dual function shaft 35. The processof the single function shaft 36 being inserted into the third dualfunction shaft 35 defines a space within the third dual function shaft35 between the closed end of the third dual function shaft 35 and fourthend cap 44; whereas, the fourth internal floating piston 48 divides thespace into the one and second cells whereby the one cell is between theouter side of the fourth internal floating piston 48 and fourth end cap44 while the second cell is between the inner side of the fourthinternal floating piston 48 and closed end of the third dual functionshaft 35. The space has a volume V_(W3) which defines the volumes of theone and second cells whereby the volumes of the one and second cellsdefine the volume V_(W3) of the fourth stage. The fourth end cap 44 isequipped with a check valve 20, the check valve 20 serves as a means toadd oil and gas to or remove oil and gas from the fourth stage. Thefourth internal floating piston 48 has a gas permeable membrane wherebythe membrane is attached to the outer side of the fourth internalfloating piston 48 and is permeable to gases but not liquids. Thepermeability allows the gas but not the oil to pass through thestructure thereby the fourth internal floating piston 48 is able toseparate the oil and gas such that the oil is able to occupy the onecell while the gas is able to occupy the second cell. The fourth end cap44 acts as a seal such that the oil and gas are confined to the one andsecond cells; and the confinement allows the oil to have a volume andgas to have both a volume and pressure whereby the gas pressure definesa force.

Referring to FIGS. 77-78, there is shown the four stage air shockwhereby each stage is equipped with the internal floating piston, inthis case emphasizing the orientation of the four stage air shock:

The four stage air shock is able to be oriented right side up or upsidedown: referring to FIG. 77, right side up defines the four stage airshock being in a vertical position such that the four stages arearranged in the descending order: first, second, third, and fourth stagewhereby the closed end of the working tube 32, first dual function shaft33, second dual function shaft 34, or third dual function shaft 35 is atthe top of the space within the working tube 32, first dual functionshaft 33, second dual function shaft 34, or third dual function 35 shaftwhile the first, second, third, or fourth end cap 41, 42, 43 or 44 is atthe bottom of the space within the working tube 32, first dual functionshaft 33, second dual function shaft 34, or third dual function shaft 35whereby the one cell is below the first, second, third, or fourthinternal floating piston 45, 46, 47, or 48 while the second cell isabove the first, second, third, or fourth internal floating piston 45,46, 47, or 48, respectively; referring to FIG. 78, upside down isopposite right side up; the opposite defines the four stage air shockbeing in a vertical position such that the four stages are arranged inthe descending order: fourth, third, second, and first stage whereby theclosed end of the working tube 32, first dual function shaft 33, seconddual function shaft 34, or third dual function shaft 35 is at the bottomof the space within the working tube 32, first dual function shaft 33,second dual function shaft 34, or third dual function 35 shaft while thefirst, second, third, or fourth end cap 41, 42, 43 or 44 is at the topof the space within the working tube 32, first dual function shaft 33,second dual function shaft 34, or third dual function shaft 35 wherebythe one cell is above the first, second, third, or fourth internalfloating piston 45, 46, 47, or 48 while the second cell is below thefirst, second, third, or fourth internal floating piston 45, 46, 47, or48, respectively.

Referring to FIGS. 79-81, there is shown the four stage air shockwhereby each stage is equipped with the internal floating piston, inthis case emphasizing the process of charging each stage with oil.Referring to FIG. 79, the four stage air shock is oriented upside downand each stage is fully compressed:

Referring to FIG. 80, the first stage is filled with gas such that thefirst stage fully extends whereby the filling is performed through thecheck valve 20, the check valve 20 is attached to the first end cap 41.The process of compressing and then filling the first stage is done inorder to purge the first stage of moisture. When the first stage fullyextends, the first spring 49 also fully extends whereby the gas, atatmospheric pressure, occupies both the one and second cells of theworking tube 32. Referring to FIG. 81, the oil charge is added throughthe check valve 20 and into the one cell of the working tube 32. Thefully extended first spring 49 positions the first internal floatingpiston 45 in a manner such that the addition of the oil charge acts tofill up the one cell whereby the gas in the second cell is atatmospheric pressure.

Referring to FIG. 80, the second stage is filled with gas such that thesecond stage fully extends whereby the filling is performed through thecheck valve 20, the check valve 20 is attached to the second end cap 42.The process of compressing and then filling the second stage is done inorder to purge the second stage of moisture. When the second stage fullyextends, the second spring 50 also fully extends whereby the gas, atatmospheric pressure, occupies both the one and second cells of thefirst dual function shaft 33. Referring to FIG. 81, the oil charge isadded through the check valve 20 and into the one cell of the first dualfunction shaft 33. The fully extended second spring 50 positions thesecond internal floating piston 46 in a manner such that the addition ofthe oil charge acts to fill up the one cell whereby the gas in thesecond cell is at atmospheric pressure.

Referring to FIG. 80, the third stage is filled with gas such that thethird stage fully extends whereby the filling is performed through thecheck valve 20, the check valve 20 is attached to the third end cap 43.The process of compressing and then filling the third stage is done inorder to purge the third stage of moisture. When the third stage fullyextends, the third spring 51 also fully extends whereby the gas, atatmospheric pressure, occupies both the one and second cells of thesecond dual function shaft 34. Referring to FIG. 81, the oil charge isadded through the check valve 20 and into the one cell of the seconddual function shaft 34. The fully extended third spring 51 positions thethird internal floating piston 47 in a manner such that the addition ofthe oil charge acts to fill up the one cell whereby the gas in thesecond cell is at atmospheric pressure.

Referring to FIG. 80, the fourth stage is filled with gas such that thefourth stage fully extends whereby the filling is performed through thecheck valve 20, the check valve 20 is attached to the fourth end cap 44.The process of compressing and then filling the fourth stage is done inorder to purge the fourth stage of moisture. When the fourth stage fullyextends, the fourth spring 52 also fully extends whereby the gas, atatmospheric pressure, occupies both the one and second cells of thethird dual function shaft 35. Referring to FIG. 81, the oil charge isadded through the check valve 20 and into the one cell of the third dualfunction shaft 35. The fully extended fourth spring 52 positions thefourth internal floating piston 48 in a manner such that the addition ofthe oil charge acts to fill up the one cell whereby the gas in thesecond cell is at atmospheric pressure.

Referring to FIGS. 82-83, there is shown the four stage air shockwhereby each stage is equipped with the internal floating piston and hasbeen charged with oil, in this case emphasizing the process of chargingeach stage with gas. The four stage air shock is oriented upside downwith each stage fully extended:

The first stage is charged with gas by adding the gas charge through thecheck valve 20 and into the one cell of the working tube 32. Since theoil and gas are immiscible, the oil does not mix with the gas and sincethe oil and gas occupy the one cell, the oil locates next to the gassuch that the surface of the oil contacts that of the gas whereby thecontacting surfaces are defined as the interface. The locations of theoil and gas at the interface are defined by density such that the moredense oil will locate below the interface next to the first internalfloating piston 45 while the less dense gas will locate above theinterface next to the first end cap 41 whereby the one cell now containsboth the oil and gas charges. The pressure of the gas charge exerts aforce on the oil; the oil is non-compressible while the first internalfloating piston 45 is impermeable to the oil thereby enabling the oil totransfer the force against the first internal floating piston 45. Thepressure of the gas charge is greater than atmospheric pressure whilethe force of the gas pressure is greater than that of the first spring49 thereby enabling the force of the gas pressure to cause the firstinternal floating piston 45 to slide downward. The downward motion ofthe first internal floating piston 45 compresses the first spring 49,decreases the volume of the second cell, and increases the pressure ofthe gas in the second cell; the downward motion continues until thepressure of the gas in the second cell is the same as that of the gascharge. Since the density of the gas is less than that of the oil, thegas in the second cell will exert a force F_(UP) that acts upwardagainst the first internal floating piston 45. Since the first internalfloating piston 45 is permeable to the gas, the upward force F_(UP)defines an increase in pressure next to the inner side of the firstinternal floating piston 45 while there is no change in pressure next tothe outer side of the first internal floating piston 45. The pressureimbalance defines a pressure differential across the structure of thefirst internal floating piston 45, the pressure differential induces anet flow of gas G_(F) through the structure of the first internalfloating piston 45 from the second cell and into the one cell. As soonas the gas from the second cell passes through the first internalfloating piston 45 into the one cell, the gas is able to bubble upwardthrough the oil and accumulate with the gas charge that is next to thefirst end cap 41 whereby the gas from the second cell and gas charge arehereafter referred to as the gas. The oil and gas do not mix togethersuch that their surfaces contact one another at the interface wherebythe more dense oil is positioned below the interface next to the firstinternal floating piston 45 while the less dense gas is positioned abovethe interface next to the first end cap 41. The combination of the flowof the gas G_(F) through the structure and the force of the gas pressurebeing greater than that of the first spring 49 causes the first internalfloating piston 45 to continue sliding downward until the first internalfloating piston 45 bottoms out against the closed end of the workingtube 32. The force of the gas pressure serves to hold the first internalfloating piston 45 against the closed end of the working tube 32 wherebythe location of the first internal floating piston 45 serves to fullycompress the first spring 49. The space within the working tube 32consists of the one cell only.

The second stage is charged with gas by adding the gas charge throughthe check valve 20 and into the one cell of the first dual functionshaft 33. Since the oil and gas are immiscible, the oil does not mixwith the gas and since the oil and gas occupy the one cell, the oillocates next to the gas such that the surface of the oil contacts thatof the gas whereby the contacting surfaces are defined as the interface.The locations of the oil and gas at the interface are defined by densitysuch that the more dense oil will locate below the interface next to thesecond internal floating piston 46 while the less dense gas will locateabove the interface next to the second end cap 42 whereby the one cellnow contains both the oil and gas charges. The pressure of the gascharge exerts a force on the oil; the oil is non-compressible while thesecond internal floating piston 46 is impermeable to the oil therebyenabling the oil to transfer the force against the second internalfloating piston 46. The pressure of the gas charge is greater thanatmospheric pressure while the force of the gas pressure is greater thanthat of the second spring 50 thereby enabling the force of the gaspressure to cause the second internal floating piston 46 to slidedownward whereby the downward motion of the second internal floatingpiston 46 compresses the second spring 50, decreases the volume of thesecond cell, and increases the pressure of the gas in the second cell;the downward motion continues until the pressure of the gas in thesecond cell is the same as that of the gas charge. Since the density ofthe gas is less than that of the oil, the gas in the second cell willexert a force F_(UP) that acts upward against the second internalfloating piston 46. Since the second internal floating piston 46 ispermeable to the gas, the upward force F_(UP) defines an increase inpressure next to the inner side of the second internal floating piston46 while there is no change in pressure next to the outer side of thesecond internal floating piston 46. The pressure imbalance defines apressure differential across the structure of the second internalfloating piston 46 whereby the pressure differential induces a net flowof gas G_(F) through the structure of the second internal floatingpiston 46 from the second cell and into the one cell. As soon as the gasfrom the second cell passes through the second internal floating piston46 into the one cell, the gas is able to bubble upward through the oiland accumulate with the gas charge that is next to the second end cap 42whereby the gas from the second cell and gas charge are hereafterreferred to as the gas. The oil and gas do not mix together such thattheir surfaces contact one another at the interface whereby the moredense oil is positioned below the interface next to the second internalfloating piston 46 while the less dense gas is positioned above theinterface next to the second end cap 42. The combination of the flow ofthe gas G_(F) through the structure and the force of the gas pressurebeing greater than that of the second spring 50 causes the secondinternal floating piston 46 to continue sliding downward until thesecond internal floating piston 46 bottoms out against the closed end ofthe first dual function shaft 33. The force of the gas pressure servesto hold the second internal floating piston 46 against the closed end ofthe first dual function shaft 33 whereby the location of the secondinternal floating piston 46 serves to fully compress the second spring50. The space within the first dual function shaft 33 consists of theone cell only.

The third stage is charged with gas by adding the gas charge through thecheck valve 20 and into the one cell of the second dual function shaft34. Since the oil and gas are immiscible, the oil does not mix with thegas and since the oil and gas occupy the one cell, the oil locates nextto the gas such that the surface of the oil contacts that of the gaswhereby the contacting surfaces are defined as the interface. Thelocations of the oil and gas at the interface are defined by densitysuch that the more dense oil will locate below the interface next to thethird internal floating piston 47 while the less dense gas will locateabove the interface next to the third end cap 43 whereby the one cellnow contains both the oil and gas charges. The pressure of the gascharge exerts a force on the oil; the oil is non-compressible while thethird internal floating piston 47 is impermeable to the oil therebyenabling the oil to transfer the force against the third internalfloating piston 47. The pressure of the gas charge is greater thanatmospheric pressure while the force of the gas pressure is greater thanthat of the third spring 51 thereby enabling the force of the gaspressure to cause the third internal floating piston 47 to slidedownward whereby the downward motion of the third internal floatingpiston 47 compresses the third spring 51, decreases the volume of thesecond cell, and increases the pressure of the gas in the second cell;the downward motion continues until the pressure of the gas in thesecond cell is the same as that of the gas charge. Since the density ofthe gas is less than that of the oil, the gas in the second cell willexert a force F_(UP) that acts upward against the third internalfloating piston 47. Since the third internal floating piston 47 ispermeable to the gas, the upward force F_(UP) defines an increase inpressure next to the inner side of the third internal floating piston 47while there is no change in pressure next to the outer side of the thirdinternal floating piston 47. The pressure imbalance defines a pressuredifferential across the structure of the third internal floating piston47 whereby the pressure differential induces a net flow of gas G_(F)through the structure of the third internal floating piston 47 from thesecond cell and into the one cell. As soon as the gas from the secondcell passes through the third internal floating piston 47 into the onecell, the gas is able to bubble upward through the oil and accumulatewith the gas charge that is next to the third end cap 43 whereby the gasfrom the second cell and gas charge are hereafter referred to as thegas. The oil and gas do not mix together such that their surfacescontact one another at the interface whereby the more dense oil ispositioned below the interface next to the third internal floatingpiston 47 while the less dense gas is positioned above the interfacenext to the third end cap 43. The combination of the flow of the gasG_(F) through the structure and the force of the gas pressure beinggreater than that of the third spring 51 causes the third internalfloating piston 47 to continue sliding downward until the third internalfloating piston 47 bottoms out against the closed end of the second dualfunction shaft 34. The force of the gas pressure serves to hold thethird internal floating piston 47 against the closed end of the seconddual function shaft 34 whereby the location of the third internalfloating piston 47 serves to fully compress the third spring 51. Thespace within the second dual function shaft 34 consists of the one cellonly.

The fourth stage is charged with gas by adding the gas charge throughthe check valve 20 and into the one cell of the third dual functionshaft 35. Since the oil and gas are immiscible, the oil does not mixwith the gas and since the oil and gas occupy the one cell, the oillocates next to the gas such that the surface of the oil contacts thatof the gas whereby the contacting surfaces are defined as the interface.The locations of the oil and gas at the interface are defined by densitysuch that the more dense oil will locate below the interface next to thefourth internal floating piston 48 while the less dense gas will locateabove the interface next to the fourth end cap 44 whereby the one cellnow contains both the oil and gas charges. The pressure of the gascharge exerts a force on the oil; the oil is non-compressible while thefourth internal floating piston 48 is impermeable to the oil therebyenabling the oil to transfer the force against the fourth internalfloating piston 48. The pressure of the gas charge is greater thanatmospheric pressure while the force of the gas pressure is greater thanthat of the fourth spring 52 thereby enabling the force of the gaspressure to cause the fourth internal floating piston 48 to slidedownward whereby the downward motion of the fourth internal floatingpiston 48 compresses the fourth spring 52, decreases the volume of thesecond cell, and increases the pressure of the gas in the second cell;the downward motion continues until the pressure of the gas in thesecond cell is the same as that of the gas charge. Since the density ofthe gas is less than that of the oil, the gas in the second cell willexert a force F_(UP) that acts upward against the fourth internalfloating piston 48. Since the fourth internal floating piston 48 ispermeable to the gas, the upward force F_(UP) defines an increase inpressure next to the inner side of the fourth internal floating piston48 while there is no change in pressure next to the outer side of thefourth internal floating piston 48. The pressure imbalance defines apressure differential across the structure of the fourth internalfloating piston 48 whereby the pressure differential induces a net flowof gas G_(F) through the structure of the fourth internal floatingpiston 48 from the second cell and into the one cell. As soon as the gasfrom the second cell passes through the fourth internal floating piston48 into the one cell, the gas is able to bubble upward through the oiland accumulate with the gas charge that is next to the fourth end cap 44whereby the gas from the second cell and gas charge are hereafterreferred to as the gas. The oil and gas do not mix together such thattheir surfaces contact one another at the interface whereby the moredense oil is positioned below the interface next to the fourth internalfloating piston 48 while the less dense gas is positioned above theinterface next to the fourth end cap 44. The combination of the flow ofthe gas G_(F) through the structure and the force of the gas pressurebeing greater than that of the fourth spring 52 causes the fourthinternal floating piston 48 to continue sliding downward until thefourth internal floating piston 48 bottoms out against the closed end ofthe third dual function shaft 35. The force of the gas pressure servesto hold the fourth internal floating piston 48 against the closed end ofthe third dual function shaft 35 whereby the location of the fourthinternal floating piston 48 serves to fully compress the fourth spring52. The space within the third dual function shaft 35 consists of theone cell only.

Referring to FIGS. 84-86, there is shown the four stage air shockwhereby each stage is equipped with the internal floating piston and hasbeen charged with oil and gas, in this case emphasizing the process ofthe internal floating piston separating the oil and gas into one and theother cells, respectively. The four stage air shock is rotated 180degrees from being upside down to right side up:

For the first stage, the rotation causes the oil and gas to reversepositions in the one cell of the working tube 32 such that the oil ispositioned below the interface next to the first end cap 41 while thegas is positioned above the interface next to the first internalfloating piston 45. Since the first internal floating piston 45 ispermeable to the gas, the gas is able to flow through the first internalfloating piston 45. The ability to flow indicates that the force of thegas pressure is able to have no effect on the first internal floatingpiston 45, and instead acts against the closed end of the working tube32. The absence of the effect cancels the force of the gas pressure thatholds the first internal floating piston 45 against the closed end ofthe working tube 32. The lack of the first internal floating piston 45being held against the closed end of the working tube 32 allows thefirst spring 49 to extend. The extension of the first spring 49 exertsthe force F_(SP) against the first internal floating piston 45 therebycausing the first internal floating piston 45 to slide downward M_(D)against the gas whereby the downward motion M_(D) creates a greaterpressure zone next to the outer side of the first internal floatingpiston 45 while an equivalent lower pressure zone is created next to theinner side of the first internal floating piston 45. The pressureimbalance defines the pressure differential across the structure of thefirst internal floating piston 45. The pressure differential induces thenet flow of gas G_(F) through the structure of the first internalfloating piston 45 from the one cell and into the second cell such thatthe oil occupies the one cell and the gas occupies the second cell.

For the second stage, the rotation causes the oil and gas to reversepositions in the one cell of the first dual function shaft 33 such thatthe oil is positioned below the interface next to the second end cap 42while the gas is positioned above the interface next to the secondinternal floating piston 46. Since the second internal floating piston46 is permeable to the gas, the gas is able to flow through the secondinternal floating piston 46. The ability to flow indicates that theforce of the gas pressure is able to have no effect on the secondinternal floating piston 46, and instead acts against the closed end ofthe first dual function shaft 33. The absence of the effect cancels theforce of the gas pressure that holds the second internal floating piston46 against the closed end of the first dual function shaft 33. The lackof the second internal floating piston 46 being held against the closedend of the first dual function shaft 33 allows the second spring 50 toextend. The extension of the second spring 50 exerts the force F_(SP)against the second internal floating piston 46 thereby causing thesecond internal floating piston 46 to slide downward M_(D) against thegas whereby the downward motion M_(D) creates a greater pressure zonenext to the outer side of the second internal floating piston 46 whilean equivalent lower pressure zone is created next to the inner side ofthe second internal floating piston 46. The pressure imbalance definesthe pressure differential across the structure of the second internalfloating piston 46. The pressure differential induces the net flow ofgas G_(F) through the structure of the second internal floating piston46 from the one cell and into the second cell such that the oil occupiesthe one cell and the gas occupies the second cell.

For the third stage, the rotation causes the oil and gas to reversepositions in the one cell of the second dual function 34 shaft such thatthe oil is positioned below the interface next to the third end cap 43while the gas is positioned above the interface next to the thirdinternal floating piston 47. Since the third internal floating piston 47is permeable to the gas, the gas is able to flow through the thirdinternal floating piston 47. The ability to flow indicates that theforce of the gas pressure is able to have no effect on the thirdinternal floating piston 47, and instead acts against the closed end ofthe second dual function 34. The absence of the effect cancels the forceof the gas pressure that holds the third internal floating piston 47against the closed end of the second dual function shaft 34. The lack ofthe third internal floating piston 47 being held against the closed endof the second dual function shaft 34 allows the third spring 51 toextend. The extension of the third spring 51 exerts the force F_(SP)against the third internal floating piston 47 thereby causing the thirdinternal floating piston 47 to slide downward M_(D) against the gaswhereby the downward motion M_(D) creates a greater pressure zone nextto the outer side of the third internal floating piston 47 while anequivalent lower pressure zone is created next to the inner side of thethird internal floating piston 47. The pressure imbalance defines thepressure differential across the structure of the third internalfloating piston 47. The pressure differential induces the net flow ofgas G_(F) through the structure of the third internal floating piston 47from the one cell and into the second cell such that the oil occupiesthe one cell and the gas occupies the second cell.

For the fourth stage, the rotation causes the oil and gas to reversepositions in the one cell of the third dual function shaft 35 such thatthe oil is positioned below the interface next to the fourth end cap 44while the gas is positioned above the interface next to the fourthinternal floating piston 48. Since the fourth internal floating piston48 is permeable to the gas, the gas is able to flow through the fourthinternal floating piston 48. The ability to flow indicates that theforce of the gas pressure is able to have no effect on the fourthinternal floating piston 48, and instead acts against the closed end ofthe third dual function shaft 35. The absence of the effect cancels theforce of the gas pressure that holds the fourth internal floating piston48 against the closed end of the third dual function shaft 35. The lackof the fourth internal floating piston 48 being held against the closedend of the third dual function shaft 35 allows the fourth spring 52 toextend. The extension of the fourth spring 52 exerts the force F_(SP)against the fourth internal floating piston 48 thereby causing thefourth internal floating piston 48 to slide downward M_(D) against thegas whereby the downward motion M_(D) creates a greater pressure zonenext to the outer side of the fourth internal floating piston 48 whilean equivalent lower pressure zone is created next to the inner side ofthe fourth internal floating piston 48. The pressure imbalance definesthe pressure differential across the structure of the fourth internalfloating piston 48. The pressure differential induces the net flow ofgas G_(F) through the structure of the fourth internal floating piston48 from the one cell and into the second cell such that the oil occupiesthe one cell and the gas occupies the second cell.

Referring to FIGS. 87-89, there is shown the four stage air shockwhereby each stage is equipped with the internal floating piston andcharged with oil and gas. The oil and gas occupy the one and secondcells, respectively, and each internal floating piston utilizes amembrane that possesses a slow permeation rate. In this case emphasis isplaced on the motion of each internal floating piston during theoperation of each stage, the operation of each stage being caused bysuspension forces acting on each stage: referring to: FIG. 87, thefirst, second, third, and fourth stages are all fully extended; FIG. 88,the first, second, third, and fourth stages are all fully compressed;and FIG. 89, the first and second stages are fully extended while thethird stage is compressed to 70% of shaft stroke and fourth stage iscompressed to 40% of shaft stroke:

Regarding operation of the first stage: (a) during compression thesuspension forces are exerted on the first dual function shaft 33thereby causing the first dual function shaft 33 to slide into theworking tube 32 whereby the sliding motion of the first dual functionshaft 33 pushes the first working piston 37 through the oil. Thesuspension forces that are exerted on the first dual function shaft 33are transferred to the oil, in turn, the suspension forces that areexerted on the oil are transferred to the first internal floating piston45, in turn, the suspension forces that are exerted on the firstinternal floating piston 45 cause the first internal floating piston 45to slide towards the closed end of the working tube 32. The motion ofthe first internal floating piston 45 decreases the volume of the secondcell whereby the decrease in the volume of the second cell refers to adecrease in the volume of the first stage and causes an increase in thegas pressure; (b) during extension the force of the gas pressure istransferred to the first internal floating piston 45, in turn, the forceof the gas pressure that is exerted on the first internal floatingpiston 45 is transferred to the oil, in turn, the force of the gaspressure that is exerted on the oil is transferred to the first dualfunction shaft 33 thereby causing the first dual function shaft 33 toslide out of the working tube 32 whereby the sliding motion of the firstdual function shaft 33 pulls the first working piston 37 through theoil. The slow permeation rate of the membrane ensures that the oil andgas remain separated and occupy the one and second cells, respectively,thereby ensuring that the force of the gas pressure is exerted on thefirst internal floating piston 45 and then transferred from the firstinternal floating piston 45 to the oil such that the first internalfloating piston 45 is able to slide away from the closed end of theworking tube 32 and move in conjunction with the first dual functionshaft 33. The motion of the first internal floating piston 45 increasesthe volume of the second cell whereby the increase in the volume refersto an increase in the volume of the first stage and causes a decrease inthe pressure of the gas. The change in pressure of the gas in the firststage causes the suspension spring movement of the first stage wherebythe suspension spring movement of the first stage is dampened by themovement of the first working piston 37 through the oil. The length ofthe first dual function shaft 33 from full extension to full compressionor vice versa refers to the first dual function shaft stroke L_(D1) orshaft stroke of the first stage L_(D1).

Regarding operation of the second stage: (a) during compression thesuspension forces are exerted on the second dual function shaft 34thereby causing the second dual function shaft 34 to slide into thefirst dual function shaft 33 whereby the sliding motion of the seconddual function shaft 34 pushes the second working piston 38 through theoil. The suspension forces that are exerted on the second dual functionshaft 34 are transferred to the oil, in turn, the suspension forces thatare exerted on the oil are transferred to the second internal floatingpiston 46, in turn, the suspension forces that are exerted on the secondinternal floating piston 46 cause the second internal floating piston 46to slide towards the closed end of the first dual function shaft 33. Themotion of the second internal floating piston 46 decreases the volume ofthe second cell whereby the decrease in the volume of the second cellrefers to a decrease in the volume of the second stage and causes anincrease in the gas pressure; (b) during extension the force of the gaspressure is transferred to the second internal floating piston 46, inturn, the force of the gas pressure that is exerted on the secondinternal floating piston 46 is transferred to the oil, in turn, theforce of the gas pressure that is exerted on the oil is transferred tothe second dual function shaft 34 thereby causing the second dualfunction shaft 34 to slide out of the first dual function shaft 33whereby the sliding motion of the second dual function shaft 34 pullsthe second working piston 38 through the oil. The slow permeation rateof the membrane ensures that the oil and gas remain separated and occupythe one and second cells, respectively, thereby ensuring that the forceof the gas pressure is exerted on the second internal floating piston 46and then transferred from the second internal floating piston 46 to theoil such that the second internal floating piston 46 is able to slideaway from the closed end of the first dual function shaft 33 and move inconjunction with the second dual function shaft 34. The motion of thesecond internal floating piston 46 increases the volume of the secondcell whereby the increase in the volume refers to an increase in thevolume of the second stage and causes a decrease in the pressure of thegas. The change in pressure of the gas in the second stage causes thesuspension spring movement of the second stage whereby the suspensionspring movement of the second stage is dampened by the movement of thesecond working piston 38 through the oil. The length of the second dualfunction shaft 34 from full extension to full compression or vice versarefers to the second dual function shaft stroke L_(D2) or shaft strokeof the second stage L_(D2).

Regarding operation of the third stage: (a) during compression thesuspension forces are exerted on the third dual function shaft 35thereby causing the third dual function shaft 35 to slide into thesecond dual function shaft 34 whereby the sliding motion of the thirddual function shaft 35 pushes the third working piston 39 through theoil. The suspension forces that are exerted on the third dual functionshaft 35 are transferred to the oil, in turn, the suspension forces thatare exerted on the oil are transferred to the third internal floatingpiston 47, in turn, the suspension forces that are exerted on the thirdinternal floating piston 47 cause the third internal floating piston 47to slide towards the closed end of the second dual function shaft 34.The motion of the third internal floating piston 47 decreases the volumeof the second cell whereby the decrease in the volume of the second cellrefers to a decrease in the volume of the third stage and causes anincrease in the gas pressure; (b) during extension the force of the gaspressure is transferred to the third internal floating piston 47, inturn, the force of the gas pressure that is exerted on the thirdinternal floating piston 47 is transferred to the oil, in turn, theforce of the gas pressure that is exerted on the oil is transferred tothe third dual function shaft 35 thereby causing the third dual functionshaft 35 to slide out of the second dual function shaft 34 whereby thesliding motion of the third dual function shaft 35 pulls the thirdworking piston 39 through the oil. The slow permeation rate of themembrane ensures that that oil and gas remain separated and occupy theone and second cells, respectively, thereby ensuring that the force ofthe gas pressure is exerted on the third internal floating piston 47 andthen transferred from the third internal floating piston 47 to the oilsuch that the third internal floating piston 47 is able to slide awayfrom the closed end of the second dual function shaft 34 and move inconjunction with the third dual function shaft 35. The motion of thethird internal floating piston 47 increases the volume of the secondcell whereby the increase in the volume refers to an increase in thevolume of the third stage and causes a decrease in the pressure of thegas. The change in pressure of the gas in the third stage causes thesuspension spring movement of the third stage whereby the suspensionspring movement of the third stage is dampened by the movement of thethird working piston 39 through the oil. The length of the third dualfunction shaft 35 from full extension to full compression or vice versarefers to the third dual function shaft stroke L_(D3) or shaft stroke ofthe third stage L_(D3).

Regarding operation of the fourth stage: (a) during compression thesuspension forces are exerted on the single function shaft 36 therebycausing the single function shaft 36 to slide into the third dualfunction shaft 35 whereby the sliding motion of the single functionshaft 36 pushes the fourth working piston 40 through the oil. Thesuspension forces that are exerted on the single function shaft 36 aretransferred to the oil, in turn, the suspension forces that are exertedon the oil are transferred to the fourth internal floating piston 48, inturn, the suspension forces that are exerted on the fourth internalfloating piston 48 cause the fourth internal floating piston 48 to slidetowards the closed end of the third dual function shaft 35. The motionof the fourth internal floating piston 48 decreases the volume of thesecond cell whereby the decrease in the volume of the second cell refersto a decrease in the volume of the fourth stage and causes an increasein the gas pressure; (b) during extension the force of the gas pressureis transferred to the fourth internal floating piston 48, in turn, theforce of the gas pressure that is exerted on the fourth internalfloating piston 48 is transferred to the oil, in turn, the force of thegas pressure that is exerted on the oil is transferred to the singlefunction shaft 36 thereby causing the single function shaft 36 to slideout of the third dual function shaft 35 whereby the sliding motion ofthe single function shaft 36 pulls the fourth working piston 40 throughthe oil. The slow permeation rate of the membrane ensures that that oiland gas remain separated and occupy the one and second cells,respectively, thereby ensuring that the force of the gas pressure isexerted on the fourth internal floating piston 48 and then transferredfrom the fourth internal floating piston 48 to the oil such that thefourth internal floating piston 48 is able to slide away from the closedend of the third dual function shaft 35 and move in conjunction with thesingle function shaft 36. The motion of the fourth internal floatingpiston 48 increases the volume of the second cell whereby the increasein the volume refers to an increase in the volume of the fourth stageand causes a decrease in the pressure of the gas. The change in pressureof the gas in the fourth stage causes the suspension spring movement ofthe fourth stage whereby the suspension spring movement of the fourthstage is dampened by the movement of the fourth working piston 40through the oil. The length of the single function shaft 36 from fullextension to full compression or vice versa refers to the singlefunction shaft stroke L_(D4) or shaft stroke of the fourth stage L_(D4).

Referring to FIGS. 90-108, there is shown the effect of the internalfloating piston on the compressed and extended lengths of the four stageair shock whereby each stage is equipped with the internal floatingpiston. For purposes of discussion, (1) the shaft refers to the first,second, or third dual function shaft or single function shaft while thecomponent refers to the working tube or first, second, or third dualfunction shaft, (2) the four stage air shock that has an internalfloating piston in each stage is referred to as the internal floatingpiston equipped four stage air shock:

The compressed and extended lengths are determined using a modified formof the one methodology that was disclosed in patent application Ser. No.14/935,423. Referring to FIGS. 90 and 91, the modification refers to theincorporation of the thickness ip_(n) of the internal floating pistoninto the set of equations used in the computations where n=1-8.Referring to FIGS. 92-97, there are shown the set of equations that areused to compute the compressed and extended lengths of the internalfloating piston equipped four stage air shock. The following dimensionsare used in the equations: extended length, EL_(X), compressed length,CL_(X), length of the working tube, L_(X), length of the nth dual orsingle function shaft, L_(Wn), shaft stroke of the nth stage, L_(Sn),thickness of the nth working piston, wp_(n), shaft shoulder, ss_(n), endcap, ec_(n), or internal floating piston, ip_(n), and thickness of themounting eyelet, me where X or n=1-8. Values are selected for the lengthof the working tube, L₁, thicknesses of the nth working piston, wp_(n),shaft shoulder, ss_(n), end cap, ec_(n), and internal floating piston,ip_(n), and thickness of the mounting eyelet, me. Referring to FIG. 108,there is shown the selected value for the length of the working tube,L₁; referring to FIGS. 100-107, there are shown the selected values forthe thicknesses of the nth working piston wp_(n), shaft shoulder ss_(n),and end cap ec_(n); referring to FIG. 98, there is shown the selectedvalue for the mounting eyelet, me; and referring to FIG. 99, there isshown the relationship between the thickness of the nth internalfloating piston, ip_(n), and that of the nth working piston, wp_(n).

Since the internal floating piston is inserted into the space within thecomponent and since the working piston and shaft shoulder are also inthe space within the component whereby the shaft is shorter than thecomponent in order to account for the thicknesses of the working pistonand shaft shoulder such that the shaft is able to slide fully into thecomponent, then the thickness of the internal floating piston must alsobe accounted for when determining the length of the shaft; inparticular, the shaft must be shorter than the component in order toaccount for the thicknesses of the working piston, shaft shoulder andinternal floating piston such that the shaft is able to slide fully intothe component. Specifically, the length of the shaft is the sum of thelength of the component less the thicknesses of the working piston,shaft shoulder, and internal floating piston plus the end cap; while,the shaft stroke of each stage is the sum of the length of eachcomponent less the thicknesses of each working piston, shaft shoulder,and internal floating piston. This way, the thickness of the internalfloating piston serves to decrease the length of the shaft or shaftstroke of each stage.

Since the extended length is computed as the sum of the compressedlength plus the shaft stroke of each stage and since the thickness ofthe internal floating piston serves to decrease the shaft stroke of eachstage, then the extended length of the internal floating piston equippedfour stage air shock is less than that of the four stage air shock.Referring to FIG. 108, there is shown the data table with values for thecompressed and extended lengths of the internal floating piston equippedfour stage air shock: for example given a compressed length of 13.50inches and that other dimensions have the same values for both theinternal floating piston equipped four stage air shock and four stageair shock, then the extended length for the internal floating pistonequipped four stage air shock is 30.50 inches while that for the fourstage air shock is 38.00 inches.

This analysis emphasizes that the incorporation of the internal floatingpiston into each stage leads to a decrease in the extended length of themultiple stage air shock. Even though the selected values for thethicknesses of each working piston, shaft shoulder, end cap, andmounting eyelet are the same, the shaft stroke of each stage must beshortened in order to account for the thickness of each internalfloating piston. Since the extended length of the multiple stage airshock is directly related to the shaft stroke of each stage, then theextended length is decreased for each internal floating piston that isincorporated into each stage of the multiple stage air shock.

Note: referring to FIGS. 98-107 and L₁ in FIG. 108, the dimensions andvalues listed therein are selected for purposes of discussion only andare not meant to imply proper values for any stage in the multiple stageair shock.

Referring to FIGS. 109-129, there is shown the effect of the internalfloating piston on the spring rate for the four stage air shock wherebyeach stage is equipped with the internal floating piston. For purposesof discussion, (1) the shaft refers to the first, second, or third dualfunction shaft or single function shaft while the component refers tothe working tube or first, second, or third dual function shaft, (2) thefour stage air shock that has an internal floating piston in each stageis referred to as the internal floating piston equipped four stage airshock, and (3) in principle, the force of the spring serves to push theshaft out of the component and indirectly increase the force of the gaspressure. However, this spring force is ignored regarding spring ratesbecause the spring is designed to create a pressure differential acrossthe structure of the internal floating piston and is not nearly strongenough to serve as a suspension spring:

The spring rate is estimated using the same second methodology that wasused for the four stage air shock disclosed in patent application Ser.No. 14/935,423; however, the selected data for the shaft strokes foreach stage in the internal floating piston equipped four stage air shockare different than those selected for each stage in the four stage airshock. Referring to FIGS. 109 and 110, the difference refers to theinternal floating piston being inserted into the space within thecomponent. When compared to the shaft stroke for each stage in the fourstage air shock, the shaft stroke for each stage in the internalfloating piston equipped four stage air shock must be shortened in orderto account for the thickness of the internal floating piston. Since theshaft stroke directly relates to the volume of the shaft stroke orvolume of the gas, then when compared to the volume of the shaft strokefor each stage in the four stage air shock the volume of the shaftstroke for each stage in the internal floating piston equipped fourstage air shock is decreased in proportion to the decrease in shaftstroke for each stage, and in turn, the volume of the gas is decreasedin proportion to the decrease in shaft stroke for each stage.

Referring to FIGS. 111-122, there is shown a set of equations used tocompute various dimensions of the internal floating piston equipped fourstage air shock. The set of equations are excerpted from patentapplication Ser. No. 14/935,423 thereby representing part of the sameequations defined in the second methodology while the dimensions and thesymbols depicting the dimensions are the same as those defined in thesecond methodology.

Referring to FIG. 123, there are shown the selected values for thediameter of each stage, D_(D1), D_(D2), D_(D3), D_(S1), shaft stroke ofeach stage, L_(D1), L_(D2), L_(D3), F_(S1), suspension force exerted oneach stage at ride height, F₁₋₄, and percent of the shaft stroke notcompressed at ride height for each stage, % L₁₋₄. The values selectedfor D_(D1), D_(D2), D_(D3), D_(S1), F₁₋₄, and % L₁₋₄ are the same asthose selected for the four stage air shock disclosed in patentapplication Ser. No. 14/935,423; whereas the values selected for L_(D1),L_(D2), L_(D3), L_(S1) are different from those selected for the fourstage air shock disclosed in patent application Ser. No. 14/935,423, thevalues being the same as those for L_(S1-4) that are computed with themodified form of the one methodology described above, respectively.

Referring to FIGS. 124-129, there are shown data tables and graphs. InFIGS. 124-127, the data tables comprise the following dimensions foreach stage in the internal floating piston equipped four stage airshock: the selected incremental shaft stroke, L_(Z), percent change inincremental shaft stroke, % ΔL_(Z), suspension force, F_(Z), change inincremental shaft stroke, ΔL_(Z), and spring rate, SR_(Z) where Z≡1e,2f, 3g, and 4h for the first, second, third, and fourth stage,respectively. In FIGS. 128 and 129, the graphs show the estimate of thespring rate for the internal floating piston equipped four stage airshock whereby the values for the suspension force F_(Z) and change inincremental shaft stroke ΔL_(Z) are used to derive the graphs. Inparticular, the values for F_(Z) for the internal floating pistonequipped four stage air shock are the same or nearly the same as thosefor the four stage air shock while the values for ΔL_(Z) for theinternal floating piston equipped four stage air shock are differentfrom those for the four stage air shock, the difference being due to thedifference in the shaft stroke L_(n).

The shortened shaft stroke L_(n) in the internal floating pistonequipped four stage air shock produces a change in incremental shaftstroke ΔL_(Z) that is less than that for the four stage air shock. Forexample referring to FIGS. 124-127, the change in incremental shaftstrokes ΔL_(Z) for the first, second, third, and fourth stages in theinternal floating piston equipped four stage air shock are 0.63, 0.48,0.35, and 0.25 while those for the first, second, third, and fourthstages in the four stage air shock are 0.71, 0.63, 0.58, and 0.53,respectively. Referring to FIGS. 128 and 129, there are shown the curvedlines 53, 54, 55, and 56 for the first, second, third, and fourth stagesin the internal floating piston equipped four stage air shock plotted ongraphs whereby the curved lines and graphs are derived with the secondmethodology. Since the change in incremental shaft stroke ΔL_(Z) is usedto determine the spacing between adjacent data points that are plottedfor each curved line, then the spacing between adjacent data points thatare plotted for each curved line for the internal floating pistonequipped four stage air shock are less than those for the four stage airshock. In principle this decreased spacing results in a graduallysloping curved line part for each stage in the internal floating pistonequipped four stage air shock being slightly steeper than that for thefour stage air shock. Yet, a comparison of the dotted line trace 57 forthe internal floating piston equipped four stage air with that for thefour stage air shock reveals that the slope of the dotted line trace 57for the internal floating piston equipped four stage air looks the sameas that for the four stage air shock. More importantly, the dotted linetrace 57 for the internal floating piston equipped four stage air isrelatively straight thereby suggesting that the spring rate for theinternal floating piston equipped four stage air shock is relativelylinear. Indeed, the shape of the dotted line trace 57 for the internalfloating piston equipped four stage air shock looks virtually the sameas for the four stage air shock.

This analysis emphasizes that given similar selected values for thedimensions of each stage in the multiple stage air shock, then theestimate of the spring rate for the internal floating piston equippedfour stage air shock is virtually the same as that for the four stageair shock. Since the selected values for the dimensions of each stage inthe internal floating piston equipped four stage air shock are the sameas that for the four stage air shock, except for shaft stroke, then theestimate is not affected by changes in the selected values of the shaftstroke. The estimate is not affected by changes in the selected valuesof the shaft stroke because the estimate is based on the computed valuesof the suspension force, F_(Z), and the computed values of F_(Z) are notaffected by changes in the selected values of the shaft strokes. Thecomputed values of F_(Z) are not affected by changes in the selectedvalues of the shaft strokes because the changes in the selected valuesof the shaft strokes cause a proportional decrease in other dimensions,or the shaft strokes are factored or canceled out in the computations ofother dimensions.

Note: referring to FIGS. 123-127, the properties and values listedtherein are selected for purposes of discussion only and are not meantto imply proper values for any stage in a multiple stage air shock.

While the invention has been illustrated and described as a shockabsorbing device with capability to separate the oil from the gas, it isnot intended to be limited to the details shown, since it will beunderstood that various omissions, modifications, substitutions andchanges in the forms and details of the device illustrated and in itsoperation can be made by those skilled in the art without departing inany way from the scope and spirit of the present invention.

What is claimed is:
 1. A gas permeable internal floating piston shockcomprising: a shaft having a cylinder-like structure with a first endand a second end; a working tube having a hollow cylinder-like structurewith a closed end and an open end, the open end is attached with an endcap configured to slidably receive the shaft; a gas permeable internalfloating piston slidably disposed within the working tube configured topermeate gases through the gas permeable internal floating piston butnot liquids, wherein the gas permeable internal floating piston is animpenetrable barrier for liquids; a working piston attached to the firstend of the shaft, the working piston slidably disposed within theworking tube between the gas permeable internal floating piston and thesecond end of the working tube; a first cell between the gas permeableinternal floating piston and the second end of the working tubeconfigured to contain liquids and gases; a second cell between the firstend of the working tube and the gas permeable internal floating pistonconfigured to contain only gases; and wherein the gas permeable internalfloating piston enables gas to permeate from the first cell to thesecond cell and from the second cell to the first cell, while providingan impenetrable barrier between the first cell and the second cell forliquids.
 2. The gas permeable internal floating piston shock of claim 1,wherein the gas permeable internal float piston comprises: a solid wall;a porous bottom attached to the solid wall; and a gas permeable membraneattached to the porous bottom.
 3. The gas permeable internal floatingpiston shock of claim 2, wherein the first cell is filled with a liquid.4. The gas permeable internal floating piston shock of claim 3, whereinthe second cell is filled with a gas.
 5. The gas permeable internalfloating piston shock of claim 4, wherein the liquid is an oil.
 6. A gaspermeable internal floating piston shock comprising: a shaft having acylinder-like structure with a first end and a second end; a workingtube having a hollow cylinder-like structure with a closed end and anopen end, the open end is attached with an end cap configured toslidably receive the shaft; a gas permeable internal floating pistonslidably disposed within the working tube comprising a gas permeablemembrane configured to permeate gases but not oils, wherein the gaspermeable membrane is an impenetrable barrier for oils, a solid wallconfigured to create a seal between the solid wall and the working tubeand configured to slide within the working tube, and a porous bottomconfigured to pass gas attached to the solid wall, wherein the gaspermeable membrane is attached to the porous bottom; a working pistonattached to the first end of the shaft, the working piston slidablydisposed within the working tube between the gas permeable internalfloating piston and the second end of the working tube; a first cellbetween the gas permeable internal floating piston and the second end ofthe working tube containing an oil; a second cell between the first endof the working tube and the gas permeable internal floating pistoncontaining a gas; and wherein the gas permeable internal floating pistonenables the gas to permeate from the first cell to the second cell andfrom the second cell to the first cell, while providing an impenetrablebarrier between the first cell and the second cell for the oil.
 7. Thegas permeable internal floating piston shock of claim 6 furthercomprises a spring attached to the gas permeable internal floatingpiston.
 8. The gas permeable internal floating piston shock of claim 7,wherein side wall comprises an inner side and an outer side.
 9. The gaspermeable internal floating piston shock of claim 8, wherein the porousbottom is attached to the outer side of the side wall creating a cup.10. The gas permeable internal floating piston shock of claim 9, whereinthe gas permeable membrane is attached to the porous bottom opposite theside wall.
 11. The gas permeable internal floating piston shock of claim10, wherein the porous bottom is a fritted disc.
 12. The gas permeableinternal floating piston shock of claim 6, wherein the gas permeablemembrane is constructed of a synthetic polymer material.
 13. The gaspermeable internal floating piston shock of claim 6, wherein the gaspermeable membrane is constructed of a silicon based material.
 14. Thegas permeable internal floating piston shock of claim 6, wherein the gaspermeable membrane is constructed of a ceramic based material.
 15. Amethod for constructing a gas permeable internal floating piston shockcomprising the steps of: providing a gas permeable internal floatingpiston shock, the gas permeable internal floating piston shockcomprising a shaft having a cylinder-like structure with a first end anda second end, a working tube having a hollow cylinder-like structurewith a closed end and an open end, the open end is attached with an endcap configured to slidably receive the shaft, a gas permeable internalfloating piston slidably disposed within the working tube configured topermeate gases through the gas permeable internal floating piston butnot liquids, wherein the gas permeable internal floating piston is animpenetrable barrier for liquids, a working piston attached to the firstend of the shaft, the working piston slidably disposed within theworking tube between the gas permeable internal floating piston and thesecond end of the working tube, a first cell between the gas permeableinternal floating piston and the second end of the working tubeconfigured to contain liquids and gases, a second cell between the firstend of the working tube and the gas permeable internal floating pistonconfigured to contain only gases, and wherein the gas permeable internalfloating piston enables gas to permeate from the first cell to thesecond cell and from the second cell to the first cell, while providingan impenetrable barrier between the first cell and the second cell forliquids; filling the first cell with a liquid; filling the first cellwith a gas; permeating the gas through the gas permeable internalfloating piston from the first cell to the second cell, while preventingthe liquid from permeating from the first cell to the second cell. 16.The method for constructing the gas permeable internal floating pistonshock of claim 15, wherein the gas permeable internal floating pistonshock further comprises a spring attached to the gas permeable internalfloating piston.
 17. The method for constructing the gas permeableinternal floating piston shock of claim 16, wherein the gas permeableinternal floating piston comprises: a solid wall; a porous bottomattached to the solid wall; and a gas permeable membrane attached to theporous bottom.
 18. The method for constructing the gas permeableinternal floating piston shock of claim 17, wherein the side wallcomprises an inner side and an outer side.
 19. The method forconstructing the gas permeable internal floating piston shock of claim18, wherein the porous bottom is attached to the outer side of the sidewall creating a cup.
 20. The method for constructing the gas permeableinternal floating piston shock of claim 19, wherein the gas permeablemembrane is attached to the porous bottom opposite the side wall.